Lithium ion secondary battery negative electrode additive, lithium ion secondary battery negative electrode slurry containing the same, and lithium ion secondary battery

Abstract

Provided are a lithium ion secondary battery negative electrode additive, and a negative electrode slurry and battery containing the same. The negative electrode additive for lithium ion secondary batteries includes polyaspartic acid salt and water. The negative electrode additive for lithium ion secondary batteries and the negative electrode slurry and battery containing the same improve the electrochemical performance of lithium ion secondary batteries, particularly the discharge capacity, charge / discharge efficiency, and capacity retention at room temperature and low temperature.

Description

[Technical field]

[0001] The present invention relates to the field of lithium ion secondary batteries, and more particularly to a lithium ion secondary battery negative electrode additive and a negative electrode slurry containing the same, and a lithium ion secondary battery. [Background technology]

[0002] In recent years, with the continuous updating of electronic technology, the need for battery devices to support the energy supply of electronic devices is also increasing. Currently, there is a demand for batteries that can store more power and output high power. Traditional lead-acid batteries and nickel-metal hydride batteries can no longer meet the needs of new electronic products. Therefore, lithium batteries have attracted attention. In the development process of lithium batteries, their capacity and performance have been improved relatively effectively.

[0003] Lithium batteries in the prior art are divided into two types: lithium metal batteries and lithium ion batteries. Lithium metal batteries use lithium metal or lithium alloy as the negative electrode, which is more dangerous and therefore is rarely used in electronic devices in daily life. Lithium ion batteries do not contain metallic lithium, and usually use lithium alloy metal oxide as the positive electrode material and graphite as the negative electrode material. However, commonly used lithium ion secondary batteries still have many disadvantages. In the prior art, the electrochemical performance of lithium ion secondary batteries, especially the cycle retention rate and discharge efficiency, are still not satisfactory. Summary of the Invention [Problem to be solved by the invention]

[0004] The main object of the present invention is to provide a negative electrode additive for lithium ion secondary batteries and a negative electrode slurry containing the same, in order to solve the problem of insufficient electrochemical performance of lithium ion secondary batteries in the prior art. [Means for solving the problem]

[0005] In order to achieve the above object, according to one embodiment of the present invention, there is provided a lithium ion secondary battery negative electrode additive comprising a polyaspartic acid salt and water.

[0006] Furthermore, in the lithium ion secondary battery negative electrode additive, the polyaspartate is selected from any one of potassium polyaspartate, sodium polyaspartate, and barium polyaspartate, or any combination thereof.

[0007] Furthermore, in the lithium ion secondary battery negative electrode additive, the content of the polyaspartate in the lithium ion secondary battery negative electrode additive is within a range of 40 wt% to 50 wt%, and the amount of insoluble matter of the polyaspartate in the lithium ion secondary battery negative electrode additive is less than 30 wt%, based on the total weight of the lithium ion secondary battery negative electrode additive.

[0008] Furthermore, in the lithium ion secondary battery negative electrode additive, the amount of insoluble matter of the polyaspartate in the lithium ion secondary battery negative electrode additive is less than 15 wt % based on the total weight of the lithium ion secondary battery negative electrode additive.

[0009] According to another aspect of the present invention, there is provided a lithium ion secondary battery anode slurry including the anode additive according to the present invention, a cathode active material, and a conductive agent.

[0010] Furthermore, in the lithium ion secondary battery negative electrode slurry, the lithium ion secondary battery negative electrode slurry contains a negative electrode additive, a negative electrode active material, an adhesive, a thickener, and a conductive agent.

[0011] Furthermore, in the lithium ion secondary battery negative electrode slurry, the amount of polyaspartate in the lithium ion secondary battery negative electrode additive is within the range of 0.05 wt % to 3 wt % based on the total weight of the negative electrode active material.

[0012] Furthermore, in the lithium ion secondary battery negative electrode slurry, the amount of polyaspartate in the lithium ion secondary battery negative electrode additive is within the range of 0.05 wt % to 0.5 wt % based on the total weight of the negative electrode active material.

[0013] Furthermore, the lithium ion secondary battery negative electrode slurry contains 85 to 95 parts by weight of a negative electrode active material, 1 to 5 parts by weight of an adhesive, 1 to 5 parts by weight of a thickener, 1 to 5 parts by weight of a conductive agent, and a predetermined amount of polyaspartic acid salt such that the amount of the polyaspartic acid salt is 0.05 wt % to 3 wt % of the total weight of the negative electrode active material.

[0014] Furthermore, in the above-mentioned lithium ion secondary battery negative electrode slurry, the negative electrode active material includes non-graphitizable carbon, graphitizable carbon, graphite, pyrolytic carbon, coke, glassy carbon, an organic polymer fired body, carbon fiber, activated carbon, and a silicon-based material-containing graphite and a silicon-based material.

[0015] According to a further aspect of the present invention, there is provided a lithium ion secondary battery including a positive electrode sheet, a negative electrode sheet, and a separator, characterized in that the lithium ion secondary battery negative electrode slurry according to the present invention is applied onto the negative electrode sheet. Effect of the Invention

[0016] The lithium ion secondary battery negative electrode additive of the present invention, the lithium ion secondary battery negative electrode slurry, and the lithium ion secondary battery having the lithium ion secondary battery negative electrode slurry of the present invention applied onto a negative electrode sheet of the present invention provide an effect of improving the electrochemical performance of the lithium ion secondary battery, in particular, the discharge capacity, charge / discharge efficiency, and capacity retention rate at room temperature and low temperature. [Brief description of the drawings]

[0017] The drawings in the specification forming a part of the present invention are used to provide a further understanding of the present invention, and the schematic embodiments of the present invention and the description thereof are used to explain the present invention and are not to be construed as unduly limiting the present invention. The drawings are as follows: [Figure 1] 1 shows the dispersion states in an aqueous medium of Examples 1 to 3 according to the present invention and Comparative Example 1. [Diagram 2] 1 shows the dispersion states in an aqueous medium of Examples 4 to 6 according to the present invention and Comparative Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] It should be noted that the embodiments of the present invention and the features of the embodiments can be combined with each other without contradiction.The present invention will be described in detail below in conjunction with the embodiments with reference to the accompanying drawings.

[0019] As described in the Background Art, the negative electrode additive for lithium ion secondary batteries in the prior art usually includes a dispersant to allow the slurry to have good dispersibility during preparation. However, the addition of the dispersant adversely reduces the electrochemical performance of the battery, particularly the cycle retention rate and discharge efficiency. In response to the problems in the prior art, an exemplary embodiment of the present invention provides a negative electrode additive for lithium ion secondary batteries, comprising a polyaspartic acid salt and water.

[0020] Unlike the lithium ion secondary battery additives in the prior art, the additive of the present invention uses polyaspartate as a dispersant. Polyaspartate is a water-soluble polymer salt in which a plurality of amino acid molecules are bonded by peptide bonds. The structure of polyaspartate contains many hydrophilic carboxyl groups, carbonyl groups, and amino groups, so polyaspartate can exert both hydrophilic and lipophilic properties and be effective as a dispersant. Surprisingly, after adding polyaspartate to the negative electrode slurry of a lithium ion secondary battery, the negative electrode active material can be well dispersed in the aqueous slurry.

[0021] A negative electrode sheet containing a negative electrode additive is prepared by the following method. A negative electrode active material and a conductive agent are uniformly mixed in an aqueous medium, then a thickener is added and stirred. Then, a lithium ion secondary battery negative electrode additive containing the polyaspartic acid salt of the present invention and water is added and stirred continuously, and finally, an adhesive is added and stirred uniformly to obtain a negative electrode slurry. The obtained negative electrode slurry is left to stand for a certain period of time, and then the obtained negative electrode slurry is applied onto a metal foil and dried at 80°C to obtain a negative electrode sheet.

[0022] In the process of preparing the negative electrode sheet, the negative electrode additive of the present invention is added, so that the negative electrode active material can be uniformly dispersed in the aqueous medium, thereby forming a negative electrode slurry with good dispersibility. Since the negative electrode slurry has uniform dispersibility, after being applied onto the metal foil, the negative electrode active material in the negative electrode slurry is uniformly distributed on the metal foil together with the conductive agent. When the obtained negative electrode sheet is used, the electrochemical performance of the lithium ion secondary battery is well improved.

[0023] In some embodiments of the present invention, the polyaspartate is selected from potassium polyaspartate, sodium polyaspartate, barium polyaspartate, or any combination thereof. In some preferred embodiments of the present invention, the polyaspartate is selected from potassium polyaspartate, sodium polyaspartate, or any combination thereof.

[0024] According to some further embodiments of the present invention, the content of the polyaspartate in the lithium ion secondary battery negative electrode additive is within the range of 40 wt% to 50 wt%, and the amount of insoluble matter of the polyaspartate is less than 30 wt% based on the total weight of the lithium ion secondary battery negative electrode additive. In a further preferred embodiment, the amount of insoluble matter of the polyaspartate is less than 15 wt% based on the total weight of the lithium ion secondary battery negative electrode additive.

[0025] The insoluble matter content (% insoluble matter) of the polyaspartate in the obtained suspension of the lithium ion secondary battery negative electrode additive is obtained by the following method: A predetermined weight of the polyaspartate (W polyaspartate) is weighed, a certain weight of deionized water (W water) is weighed, and mixed to obtain the negative electrode additive, the obtained negative electrode additive suspension is filtered and dried until the obtained solid matter reaches a certain weight, and the weight of the obtained dry solid matter (W solid matter) is weighed and calculated by the following calculation. % Insolubles = (W Solids / (W Polyaspartate + W Water)) * 100%.

[0026] If the content of polyaspartate in the lithium ion secondary battery negative electrode additive is less than 40wt%, the content of polyaspartate is insufficient to effectively realize the dispersion effect, and if the content of polyaspartate in the lithium ion secondary battery negative electrode additive is more than 50wt%, the excess polyaspartate will adversely affect the conductivity of the battery.

[0027] Based on the total weight of the lithium ion secondary battery negative electrode additive, when the amount of insoluble matter of the polyaspartate in the lithium ion secondary battery negative electrode additive exceeds 30wt%, the water solubility of the polyaspartate is obviously insufficient, and effective dispersion effect cannot be achieved. In different embodiments of the present invention, based on the total weight of the lithium ion secondary battery negative electrode additive, the amount of insoluble matter of the polyaspartate in the lithium ion secondary battery negative electrode additive is less than 25wt%, less than 20wt%, less than 15wt%, less than 10wt%, less than 7wt%, less than 6wt%, less than 5wt%, less than 4wt%, less than 3wt%, or less than 2wt%.

[0028] In another embodiment of the present invention, in the lithium ion secondary battery negative electrode additive, the content of polyaspartate and the amount of insoluble matter of the polyaspartate may be such that the content of polyaspartate is more than 42 wt%, and the amount of insoluble matter of the polyaspartate is less than 25 wt%, based on the total weight of the lithium ion secondary battery negative electrode additive; the content of polyaspartate is more than 45 wt%, and the amount of insoluble matter of the polyaspartate is less than 20 wt%, based on the total weight of the lithium ion secondary battery negative electrode additive; the content of polyaspartate is more than 47 wt%, and the amount of insoluble matter of the polyaspartate is less than 15 wt%, based on the total weight of the lithium ion secondary battery negative electrode additive; The polyaspartate content may be greater than 42 wt%, and the amount of insoluble matter of the polyaspartate may be less than 10 wt%, based on the total weight of the lithium ion secondary battery negative electrode additive; the polyaspartate content may be greater than 40 wt%, and the amount of insoluble matter of the polyaspartate may be less than 5 wt%, based on the total weight of the lithium ion secondary battery negative electrode additive; the polyaspartate content may be greater than 46 wt%, and the amount of insoluble matter of the polyaspartate may be less than 3 wt%, based on the total weight of the lithium ion secondary battery negative electrode additive; or the polyaspartate content may be greater than 40 wt%, and the amount of insoluble matter of the polyaspartate may be less than 2 wt%, based on the total weight of the lithium ion secondary battery negative electrode additive.

[0029] According to another exemplary embodiment of the present invention, there is provided a lithium ion secondary battery negative electrode slurry comprising the negative electrode additive of the present invention, a negative electrode active material, and a conductive agent, wherein the negative electrode additive comprises a polyaspartate salt and water.

[0030] In a preferred embodiment of the present invention, the negative electrode slurry of a lithium ion secondary battery includes the negative electrode additive of the present application, a negative electrode active material, an adhesive, a thickener, and a conductive agent, and the negative electrode additive includes polyaspartate and water. In this embodiment, when preparing the negative electrode slurry, the negative electrode additive containing polyaspartate and water is added to the mixed slurry of the negative electrode active material, the conductive agent, and the thickener at the same time, and finally the adhesive is added and stirred uniformly to obtain the negative electrode slurry.

[0031] According to a further preferred embodiment of the present invention, there is provided a lithium ion secondary battery including a positive electrode sheet, a negative electrode sheet, and a separator, in which the lithium ion secondary battery negative electrode slurry according to the present invention is applied onto the negative electrode sheet.

[0032] Since the polyaspartate acts as a dispersant and thus promotes the dispersibility of the slurry, the polyaspartate and the polyaspartate can be mutually promoted to provide a better dispersibility in the negative electrode slurry of the present invention. In addition, since the polyaspartate is a long-chain polymer, an entanglement phenomenon occurs during the process of drying the slurry to obtain a negative electrode sheet, and the adhesive effect of the slurry to the metal foil is increased. After being applied onto the metal foil, the conductive agent in the negative electrode slurry of the present invention is uniformly distributed on the metal foil due to its uniform dispersibility. When the negative electrode sheet obtained by the present invention is used, the electrochemical performance of the lithium ion secondary battery is improved.

[0033] In the above embodiment, the polyaspartate is selected from one of potassium polyaspartate, sodium polyaspartate, barium polyaspartate, or any combination thereof. In some preferred embodiments of the present invention, the polyaspartate is selected from one of potassium polyaspartate, sodium polyaspartate, or a combination thereof.

[0034] In some embodiments, the amount of polyaspartate in the lithium ion secondary battery negative electrode additive is in the range of 0.05wt% to 3wt% based on the total weight of the negative electrode active material. The negative electrode slurry of the lithium ion secondary battery is usually composed of a negative electrode active material, an adhesive, a thickener, and a conductive agent, and the polyaspartate used in the present invention is used to effectively disperse the negative electrode active material. As a result of a large number of experiments, the inventors have found that within the above-mentioned range of additive amount, the negative electrode active material can be uniformly dispersed in the negative electrode slurry and the effects of other components (adhesive, thickener, conductive agent, etc.) are not adversely affected.

[0035] In some embodiments of the present invention, the amount of polyaspartate in the lithium ion secondary battery negative electrode additive may be within the range of 0.05 wt%, 0.06 wt%, 0.07 wt%, 0.1 wt%, 0.15 wt%, 0.2 wt%, 0.25 wt%, 0.5 wt%, 0.75 wt%, 1 wt%, 1.25 wt%, 1.5 wt%, 1.75 wt%, 2 wt%, 2.25 wt%, 2.5 wt%, 2.75 wt%, and the amount of polyaspartate in the lithium ion secondary battery negative electrode additive may be within the range of 2.5 wt%, 2.6 wt%, 2.7 wt%, 2.8 wt%, 2.9 wt%, 3 wt% of the total weight of the negative electrode active material for different combinations.

[0036] Specifically, the amount of polyaspartate added in the lithium ion secondary battery negative electrode additive is 0.05 wt% to 3 wt%, 0.06 wt% to 3 wt%, 0.07 wt% to 3 wt%, 0.08 wt% to 3 wt%, 0.09 wt% to 3 wt%, 0.1 wt% to 3 wt%, 0.15 wt% to 3 wt%, 0.2 wt% to 3 wt%, 0.25 wt% to 3 wt%, 0.3 wt% to 3 wt%, 0.5 wt% to 3 wt%, 0.75 wt% to 3 wt%, 1 wt% to 3 wt%, 1 wt% to 2 wt%, 1.25 wt% to 3 wt%, 1.5 wt% to 3 wt%, %, 1.75wt% to 3wt%, 2wt% to 3wt%, 2.25wt% to 3wt%, 2.5wt% to 3wt%, 2.75wt% to 3wt%, 0.05wt% to 0.3wt%, 0.06wt% to 0.3wt%, 0.07wt% to 0.3wt%, 0.08wt% to 0.3wt%, 0.09wt% to 0.3wt%, 0.1wt% to 0.3wt%, 0.3wt% to 0.5wt%, 0.3wt% to 0.6wt%, 0.3wt% to 0.7wt%, 0.3wt% to 0.8wt%, 0.3wt% to 0.9wt%, 0.3wt% to 1.0wt%.

[0037] In the above embodiment, the lithium ion secondary battery negative electrode slurry preferably contains 85 to 95 parts by weight of a negative electrode active material, 1 to 5 parts by weight of an adhesive, 1 to 5 parts by weight of a thickener, 1 to 5 parts by weight of a conductive agent, and a predetermined amount of polyaspartate such that the amount of polyaspartate is 0.05 wt% to 5 wt% of the total weight of the negative electrode active material. Within the above numerical range, the negative electrode slurry of the present invention can be prepared with an optimal blending ratio, and the formed negative electrode slurry can exhibit good dispersibility.

[0038] In some embodiments of the present invention, the negative electrode active material contained in the negative electrode slurry of the present invention includes graphite containing a silicon-based material. The negative electrode active material includes one or more negative electrode materials capable of absorbing and releasing lithium as the negative electrode active material. Examples of the negative electrode material capable of absorbing and releasing lithium include carbon materials and silicon-based materials such as non-graphitizable carbon, easily graphitizable carbon, graphite, pyrolytic carbon, coke, glassy carbon, organic polymer sintered body, carbon fiber, activated carbon, silicon-oxygen-based material, silicon-carbon-based material (e.g., graphite containing a silicon-based material), or silicon alloy. In these materials, examples of coke include pitch coke, needle coke, and petroleum coke. The organic polymer sintered body is obtained by roasting and carbonizing a polymer material such as a phenolic resin or a furan resin at an appropriate temperature. Some organic polymer sintered bodies are classified into non-graphitizable carbon and easily graphitizable carbon. Preferably, it is graphite containing a silicon-based material. EXAMPLES

[0039] The present invention will now be described in more detail in conjunction with specific examples, but these examples should not be construed as limiting the scope of the present invention.

[0040] The dispersion effect of the lithium ion secondary battery negative electrode additive of the present application in the electrode active material was observed in the following Examples 1 to 6 and Comparative Examples 1 and 2. Figures 1 and 2 show the apparent dispersion states of Examples 1 to 3 and Comparative Example 1 (Figure 1), and Examples 4 to 6 and Comparative Example 2 (Figure 2), respectively, photographed by a camera.

[0041] Example 1 1) Preparation of lithium ion secondary battery negative electrode additive: 40g of sodium polyaspartate was taken and added to 60g of water while stirring to prepare a suspension of lithium ion secondary battery negative electrode additive. When measured, the insoluble matter content of the sodium polyaspartate was 1%. Thus, a lithium ion secondary battery negative electrode additive was prepared in which the content of sodium polyaspartate was 40% and the insoluble matter content of sodium polyaspartate was 1%. 2) Preparation of lithium ion secondary battery negative electrode slurry: 0.15 g of the lithium ion secondary battery negative electrode additive containing sodium polyaspartate (containing 0.06 g of sodium polyaspartate) prepared in step 1) was taken, stirred and added to 15 g of water, and then 3 g of graphite active material was added to the aqueous solution of the lithium ion secondary battery negative electrode additive, and stirred until the graphite active material at the bottom was stirred to form a suspension, and the suspension was allowed to stand for 30 minutes, after which the dispersion phenomenon was observed.

[0042] Example 2 1) Preparation of lithium ion secondary battery negative electrode additive: 40g of potassium polyaspartate was taken and added to 60g of water while stirring to prepare a suspension of lithium ion secondary battery negative electrode additive. When measured, the insoluble matter content of the potassium polyaspartate was 2%. Thus, a lithium ion secondary battery negative electrode additive was prepared in which the potassium polyaspartate content was 40% and the insoluble matter content of the potassium polyaspartate was 2%. 2) Preparation of lithium ion secondary battery negative electrode slurry: Take 0.15g of the lithium ion secondary battery negative electrode additive containing potassium polyaspartate (containing 0.06g of potassium polyaspartate) prepared in step 1), stir and add to 15g of water, then add 3g of graphite active material to the aqueous solution of the lithium ion secondary battery negative electrode additive, stir until the graphite active material at the bottom is stirred to form a suspension, and leave the suspension to stand for 30 minutes, after which observe the dispersion phenomenon.

[0043] Example 3 1) Preparation of lithium ion secondary battery negative electrode additive: 20g of potassium polyaspartate and 20g of sodium polyaspartate were taken and added to 60g of water while stirring to prepare a suspension of lithium ion secondary battery negative electrode additive. When measured, the insoluble matter content of the polyaspartate was 2%. Thus, a lithium ion secondary battery negative electrode additive was prepared in which the polyaspartate content was 40% and the insoluble matter content of the potassium polyaspartate was 2%. 2) Preparation of lithium ion secondary battery negative electrode slurry: 0.15 g of the lithium ion secondary battery negative electrode additive containing polyaspartate prepared in step 1) (containing 0.06 g of polyaspartate) was taken and added to 15 g of water with stirring, then 3 g of graphite active material was added to the aqueous solution of the lithium ion secondary battery negative electrode additive, and stirring was continued until the graphite active material at the bottom was stirred to form a suspension, and the suspension was allowed to stand for 30 minutes, after which the dispersion phenomenon was observed.

[0044] Comparative Example 1 3 g of the graphite active material was directly added to 15 g of water, stirred until the graphite active material at the bottom was stirred to form a suspension, and then allowed to stand for 30 minutes, after which the dispersion phenomenon was observed.

[0045] Example 4 1) Preparation of lithium ion secondary battery negative electrode additive: 40g of sodium polyaspartate was taken and added to 60g of water while stirring to prepare a suspension of lithium ion secondary battery negative electrode additive. When measured, the insoluble matter content of the sodium polyaspartate was 1%. Thus, a lithium ion secondary battery negative electrode additive was prepared in which the content of sodium polyaspartate was 40% and the insoluble matter content of sodium polyaspartate was 1%. 2) Preparation of lithium ion secondary battery negative electrode slurry: Take 0.15g of the lithium ion secondary battery negative electrode additive containing sodium polyaspartate (containing 0.06g of sodium polyaspartate) prepared in step 1), stir and add it to 15g of water, then add 3g of silicon monoxide material to the aqueous solution of lithium ion secondary battery negative electrode additive, continue to stir until the silicon monoxide material at the bottom is stirred to form a suspension, and allow the suspension to stand for 30 minutes, after which observe the dispersion phenomenon.

[0046] Example 5 1) Preparation of lithium ion secondary battery negative electrode additive: 40g of potassium polyaspartate was taken and added to 60g of water while stirring to prepare a suspension of lithium ion secondary battery negative electrode additive. When measured, the insoluble matter content of the potassium polyaspartate was 2%. Thus, a lithium ion secondary battery negative electrode additive was prepared in which the potassium polyaspartate content was 40% and the insoluble matter content of the potassium polyaspartate was 2%. 2) Preparation of lithium ion secondary battery negative electrode slurry: Take 0.15g of the lithium ion secondary battery negative electrode additive containing potassium polyaspartate (containing 0.06g of potassium polyaspartate) prepared in step 1), stir and add it to 15g of water, then add 3g of silicon monoxide material to the aqueous solution of lithium ion secondary battery negative electrode additive, continue to stir until the silicon monoxide material at the bottom is stirred to form a suspension, and allow the suspension to stand for 30 minutes, after which observe the dispersion phenomenon.

[0047] Example 6 1) Preparation of lithium ion secondary battery negative electrode additive: 20g of potassium polyaspartate and 20g of sodium polyaspartate were taken and added to 60g of water while stirring to prepare a suspension of lithium ion secondary battery negative electrode additive. When measured, the insoluble matter content of the polyaspartate was 2%. Thus, a lithium ion secondary battery negative electrode additive was prepared in which the polyaspartate content was 40% and the insoluble matter content of the polyaspartate was 2%. 2) Preparation of lithium ion secondary battery negative electrode slurry: Take 0.15 g of the lithium ion secondary battery negative electrode additive containing polyaspartate prepared in step 1) (containing 0.06 g of polyaspartate), stir and add to 15 g of water, then add 3 g of silicon monoxide active material to the aqueous solution of the lithium ion secondary battery negative electrode additive, continue to stir until the graphite active material at the bottom is stirred to form a suspension, and allow the suspension to stand for 30 minutes, after which observe the dispersion phenomenon.

[0048] Comparative Example 2 3g of silicon monoxide material was directly added to 15g of water, stirred until the silicon monoxide material at the bottom was stirred to form a suspension, and then allowed to stand for 30 minutes, after which the dispersion phenomenon was observed.

[0049] For the experimental results of dispersion in water of the electrode active materials of Examples 1 to 6 and Comparative Examples 1 and 2 of the present invention, refer to Figs. 1 and 2, respectively. Here, Fig. 1 shows the experimental results of dispersion in water of the electrode active materials of Examples 1 to 3 and Comparative Example 1, and Fig. 2 shows the experimental results of dispersion in water of the electrode active materials of Examples 4 to 6 and Comparative Example 2.

[0050] As can be seen from the above examples and comparative examples, in Examples 1 to 6 of the present invention in which potassium polyaspartate and / or sodium polyaspartate were added to prepare the lithium ion secondary battery negative electrode additive, the electrode active material was well dispersed in the solvent to form a suspension. On the other hand, the negative electrode active materials of Comparative Examples 1 to 2 in which no additive was added were suspended on the surface of the solvent, and as is clear from the result of Comparative Example 1, the graphite active material was aggregated in large amounts, and in Comparative Example 2, the silicon monoxide negative electrode active material was relatively largely aggregated on the surface of the aqueous solvent. Therefore, when the additive of the present invention is used, a polyaspartate selected from potassium polyaspartate or sodium polyaspartate can effectively reduce the surface tension of the electrode active material or other substances required to be added to the negative electrode in the aqueous solvent, thereby contributing to the dispersion of the electrode active material in the electrode slurry, and finally, various substances such as electrode active material, conductive agent, and binder can be uniformly dispersed in the electrode material prepared.

[0051] In the following examples and comparative examples, a lithium ion secondary battery negative electrode additive is prepared using a polyaspartic acid salt, and then the prepared lithium ion secondary battery negative electrode slurry is applied to a lithium ion secondary battery negative electrode sheet and dried to obtain a lithium ion secondary battery negative electrode sheet, thereby improving the battery performance.

[0052] Example 7 1) Preparation of negative electrode sheet: 93g of silicon-based material-containing graphite (negative electrode active material) and 1.5g of conductive agent Super-p were weighed and mixed uniformly, 2g of thickener carboxymethylcellulose (CMC) was added, deionized water was added and stirred for 15 minutes, then 5.58g of deionized aqueous solution / suspension containing sodium polyaspartate obtained below (negative electrode additive) was added, where the amount of sodium polyaspartate added was 2.79g (3wt% based on the total weight of active material), (wherein the content of sodium polyaspartate in the deionized aqueous solution / suspension of sodium polyaspartate was 50%, and the amount of insoluble matter of sodium polyaspartate in the aqueous solution / suspension was 5%) was kept stirring for 30 minutes, and finally 3.5g of adhesive styrene butadiene rubber (SBR) was added and stirred for 30 minutes to obtain negative electrode slurry. The obtained negative electrode slurry was allowed to stand for 1 hour, and then the obtained slurry was applied onto a copper foil and dried at 80° C. to obtain a negative electrode sheet. 2) Battery assembly and testing: The obtained negative electrode sheet was placed in a vacuum oven at a temperature of 100°C and a vacuum of -90kPa to dry. After drying for 5 hours, the negative electrode sheet was removed from the vacuum oven, and after the negative electrode plate was cooled, it was subjected to subsequent processing such as cutting, roll pressing, and die cutting. The negative and positive electrode sheets were then assembled together to form a button-type half cell, and an electrolyte solution with a LiPF6 concentration of 1.08 mol / kg was injected into the experimental battery. Initial capacity and efficiency tests were performed at 25°C, followed by a low-temperature capacity test at 10°C with a current of 0.5C, a discharge ratio performance test at a discharge current of 3C, and a room-temperature cycle performance test at a current of 1C. The experimental results are shown in Table 1.

[0053] Example 8 1) Preparation of negative electrode sheet: 93g of silicon-based material-containing graphite (negative electrode active material) and 1.5g of conductive agent Super-p were weighed and mixed uniformly, 2g of thickener carboxymethylcellulose (CMC) was added, deionized water was added and stirred for 15 minutes, then 0.1175g of deionized aqueous solution / suspension containing sodium polyaspartate obtained below (negative electrode additive) was added, where the amount of sodium polyaspartate added was 0.047g (0.05wt% based on the total weight of active material), (wherein the content of sodium polyaspartate in the deionized aqueous solution / suspension of sodium polyaspartate is 40%, and the amount of insoluble matter of sodium polyaspartate in the aqueous solution / suspension is 2%) was added, and stirring was continued for 30 minutes, and finally 3.5g of adhesive styrene butadiene rubber (SBR) was added and stirring was continued for 30 minutes to obtain negative electrode slurry. The obtained negative electrode slurry was allowed to stand for 1 hour, and then the obtained slurry was applied onto a copper foil and dried at 80° C. to obtain a negative electrode sheet. 2) Battery assembly and testing: The obtained negative electrode sheet was placed in a vacuum oven at a temperature of 100°C and a vacuum of -90kPa to dry. After drying for 5 hours, the negative electrode sheet was removed from the vacuum oven, and after the negative electrode plate was cooled, it was subjected to subsequent processing such as cutting, roll pressing, and die cutting. The negative and positive electrode sheets were then assembled together to form a button-type half cell, and an electrolyte solution with a LiPF6 concentration of 1.08 mol / kg was injected into the experimental battery. Initial capacity and efficiency tests were performed at 25°C, followed by a low-temperature capacity test at 10°C with a current of 0.5C, a discharge ratio performance test at a discharge current of 3C, and a room-temperature cycle performance test at a current of 1C. The experimental results are shown in Table 1.

[0054] Example 9 1) Preparation of negative electrode sheet: 93g of silicon-based material-containing graphite (negative electrode active material) and 1.5g of conductive agent Super-p were weighed and mixed uniformly, 2g of thickener carboxymethylcellulose (CMC) was added, deionized water was added and stirred for 15 minutes, then 0.558g of deionized aqueous solution / suspension containing sodium polyaspartate obtained below (negative electrode additive) was added, where the amount of sodium polyaspartate added was 0.279g (0.3wt% based on the total weight of active material), (wherein the content of sodium polyaspartate in the deionized aqueous solution / suspension of sodium polyaspartate is 50%, and the amount of insoluble matter of sodium polyaspartate in the aqueous solution / suspension is 1%) was continuously stirred for 30 minutes, and finally 3.5g of adhesive styrene butadiene rubber (SBR) was added and stirred for 30 minutes to obtain negative electrode slurry. The obtained negative electrode slurry was allowed to stand for 1 hour, and then the obtained slurry was applied onto a copper foil and dried at 80° C. to obtain a negative electrode sheet. 2) Battery assembly and testing: The obtained negative electrode sheet was placed in a vacuum oven at a temperature of 100°C and a vacuum of -90kPa to dry. After drying for 5 hours, the negative electrode sheet was removed from the vacuum oven, and after the negative electrode plate was cooled, it was subjected to subsequent processing such as cutting, roll pressing, and die cutting. The negative and positive electrode sheets were then assembled together to form a button-type half cell, and an electrolyte solution with a LiPF6 concentration of 1.08 mol / kg was injected into the experimental battery. Initial capacity and efficiency tests were performed at 25°C, followed by a low-temperature capacity test at 10°C with a current of 0.5C, a discharge ratio performance test at a discharge current of 3C, and a room-temperature cycle performance test at a current of 1C. The experimental results are shown in Table 1.

[0055] Example 10 1) Preparation of negative electrode sheet: 93g of silicon-based material-containing graphite (negative electrode active material) and 1.5g of conductive agent Super-p were weighed and mixed uniformly, 2g of thickener carboxymethylcellulose (CMC) was added, deionized water was added and stirred for 15 minutes, then 1.1625g of deionized aqueous solution / suspension containing sodium polyaspartate obtained below (negative electrode additive) was added, where the amount of sodium polyaspartate added was 0.465g (0.5wt% based on the total weight of active material), (wherein the content of sodium polyaspartate in the deionized aqueous solution / suspension of sodium polyaspartate is 40%, and the amount of insoluble matter of sodium polyaspartate in the aqueous solution / suspension is 3%) was kept stirring for 30 minutes, and finally 3.5g of adhesive styrene butadiene rubber (SBR) was added and stirred for 30 minutes to obtain negative electrode slurry. The obtained negative electrode slurry was allowed to stand for 1 hour, and then the obtained slurry was applied onto a copper foil and dried at 80° C. to obtain a negative electrode sheet. 2) Battery assembly and testing: The obtained negative electrode sheet was placed in a vacuum oven at a temperature of 100°C and a vacuum of -90kPa to dry. After drying for 5 hours, the negative electrode sheet was removed from the vacuum oven, and after the negative electrode plate was cooled, it was subjected to subsequent processing such as cutting, roll pressing, and die cutting. The negative and positive electrode sheets were then assembled together to form a button-type half cell, and an electrolyte solution with a LiPF6 concentration of 1.08 mol / kg was injected into the experimental battery. Initial capacity and efficiency tests were performed at 25°C, followed by a low-temperature capacity test at 10°C with a current of 0.5C, a discharge ratio performance test at a discharge current of 3C, and a room-temperature cycle performance test at a current of 1C. The experimental results are shown in Table 1.

[0056] Comparative Example 3 1) Preparation of negative electrode sheet: 93g of silicon-based material-containing graphite (negative electrode active material) and 1.5g of conductive agent Super-p were weighed and mixed uniformly, 2g of thickener carboxymethyl cellulose (CMC) was added, deionized water was added and stirred for 15 minutes, and finally 3.5g of adhesive styrene butadiene rubber (SBR) was added and stirred for 30 minutes to obtain negative electrode slurry. After leaving the obtained negative electrode slurry for 1 hour, the obtained slurry was applied onto copper foil and dried at 80°C to obtain a negative electrode sheet. 2) Battery assembly and testing: The obtained negative electrode sheet was placed in a vacuum oven at a temperature of 100°C and a vacuum of -90kPa to dry. After drying for 5 hours, the negative electrode sheet was removed from the vacuum oven, and after the negative electrode plate was cooled, it was subjected to subsequent processing such as cutting, roll pressing, and die cutting. The negative and positive electrode sheets were then assembled together to form a button-type half cell, and an electrolyte solution with a LiPF6 concentration of 1.08 mol / kg was injected into the experimental battery. Initial capacity and efficiency tests were performed at 25°C, followed by a low-temperature capacity test at 10°C with a current of 0.5C, a discharge ratio performance test at a discharge current of 3C, and a room-temperature cycle performance test at a current of 1C. The experimental results are shown in Table 1.

[0057] Comparative Example 4 1) Preparation of negative electrode sheet: 93g of silicon-based material-containing graphite (negative electrode active material) and 1.5g of conductive agent Super-p were weighed and mixed uniformly, 2g of thickener carboxymethylcellulose (CMC) was added, deionized water was added and stirred for 15 minutes, then 11.625g of deionized aqueous solution / suspension containing sodium polyaspartate obtained below (negative electrode additive) was added, where the amount of sodium polyaspartate added was 4.65g (5wt% based on the total weight of active material), (wherein the content of sodium polyaspartate in the deionized aqueous solution / suspension of sodium polyaspartate was 40%, and the amount of insoluble matter of sodium polyaspartate in the aqueous solution / suspension was 1%) was kept stirring for 30 minutes, and finally 3.5g of adhesive styrene butadiene rubber (SBR) was added and stirred for 30 minutes to obtain negative electrode slurry. The obtained negative electrode slurry was allowed to stand for 1 hour, and then the obtained slurry was applied onto a copper foil and dried at 80° C. to obtain a negative electrode sheet. 2) Battery assembly and testing: The obtained negative electrode sheet was placed in a vacuum oven at a temperature of 100°C and a vacuum of -90kPa to dry. After drying for 5 hours, the negative electrode sheet was removed from the vacuum oven, and after the negative electrode plate was cooled, it was subjected to subsequent processing such as cutting, roll pressing, and die cutting. The negative and positive electrode sheets were then assembled together to form a button-type half cell, and an electrolyte solution with a LiPF6 concentration of 1.08 mol / kg was injected into the experimental battery. Initial capacity and efficiency tests were performed at 25°C, followed by a low-temperature capacity test at 10°C with a current of 0.5C, a discharge ratio performance test at a discharge current of 3C, and a room-temperature cycle performance test at a current of 1C. The experimental results are shown in Table 1.

[0058] Example 11 1) Preparation of negative electrode sheet: 93g of silicon-based material-containing graphite (negative electrode active material) and 1.5g of conductive agent Super-p were weighed and mixed uniformly, 2g of thickener carboxymethylcellulose (CMC) was added, deionized water was added and stirred for 15 minutes, then 5.58g of deionized aqueous solution / suspension containing potassium polyaspartate obtained below (negative electrode additive) was added, where the amount of potassium polyaspartate added was 2.79g (3wt% based on the total weight of active material), (wherein the content of potassium polyaspartate in the deionized aqueous solution / suspension of potassium polyaspartate was 50%, and the amount of insoluble matter of potassium polyaspartate in the aqueous solution / suspension was 5%) was kept stirring for 30 minutes, and finally 3.5g of adhesive styrene butadiene rubber (SBR) was added and stirred for 30 minutes to obtain negative electrode slurry. The obtained negative electrode slurry was allowed to stand for 1 hour, and then the obtained slurry was applied onto a copper foil and dried at 80° C. to obtain a negative electrode sheet. 2) Battery assembly and testing: The obtained negative electrode sheet was placed in a vacuum oven at a temperature of 100°C and a vacuum of -90kPa to dry. After drying for 5 hours, the negative electrode sheet was removed from the vacuum oven, and after the negative electrode plate was cooled, it was subjected to subsequent processing such as cutting, roll pressing, and die cutting. The negative and positive electrode sheets were then assembled together to form a button-type half cell, and an electrolyte solution with a LiPF6 concentration of 1.08 mol / kg was injected into the experimental battery. Initial capacity and efficiency tests were performed at 25°C, followed by a low-temperature capacity test at 10°C with a current of 0.5C, a discharge ratio performance test at a discharge current of 3C, and a room-temperature cycle performance test at a current of 1C. The experimental results are shown in Table 1.

[0059] Example 12 1) Preparation of negative electrode sheet: 93g of silicon-based material-containing graphite (negative electrode active material) and 1.5g of conductive agent Super-p were weighed and mixed uniformly, 2g of thickener carboxymethylcellulose (CMC) was added, deionized water was added and stirred for 15 minutes, then 0.1175g of deionized aqueous solution / suspension containing potassium polyaspartate obtained below (negative electrode additive) was added, where the amount of potassium polyaspartate added was 0.047g (0.05wt% based on the total weight of active material), (wherein the content of potassium polyaspartate in the deionized aqueous solution / suspension of potassium polyaspartate is 40%, and the amount of insoluble matter of potassium polyaspartate in the aqueous solution / suspension is 2%) was added, and stirring was continued for 30 minutes, and finally 3.5g of adhesive styrene butadiene rubber (SBR) was added and stirring was continued for 30 minutes to obtain negative electrode slurry. The obtained negative electrode slurry was allowed to stand for 1 hour, and then the obtained slurry was applied onto a copper foil and dried at 80° C. to obtain a negative electrode sheet. 2) Battery assembly and testing: The obtained negative electrode sheet was placed in a vacuum oven at a temperature of 100°C and a vacuum of -90kPa to dry. After drying for 5 hours, the negative electrode sheet was removed from the vacuum oven, and after the negative electrode plate was cooled, it was subjected to subsequent processing such as cutting, roll pressing, and die cutting. The negative and positive electrode sheets were then assembled together to form a button-type half cell, and an electrolyte solution with a LiPF6 concentration of 1.08 mol / kg was injected into the experimental battery. Initial capacity and efficiency tests were performed at 25°C, followed by a low-temperature capacity test at 10°C with a current of 0.5C, a discharge ratio performance test at a discharge current of 3C, and a room-temperature cycle performance test at a current of 1C. The experimental results are shown in Table 1.

[0060] Example 13 1) Preparation of negative electrode sheet: 93g of silicon-based material-containing graphite (negative electrode active material) and 1.5g of conductive agent Super-p were weighed and mixed uniformly, 2g of thickener carboxymethylcellulose (CMC) was added, deionized water was added and stirred for 15 minutes, then 0.558g of deionized aqueous solution / suspension containing potassium polyaspartate obtained below (negative electrode additive) was added, where the amount of potassium polyaspartate added was 0.279g (0.3wt% based on the total weight of active material), (wherein the content of potassium polyaspartate in the deionized aqueous solution / suspension of potassium polyaspartate is 50%, and the amount of insoluble matter of potassium polyaspartate in the aqueous solution / suspension is 1%) was continuously stirred for 30 minutes, and finally 3.5g of adhesive styrene butadiene rubber (SBR) was added and stirred for 30 minutes to obtain negative electrode slurry. The obtained negative electrode slurry was allowed to stand for 1 hour, and then the obtained slurry was applied onto a copper foil and dried at 80° C. to obtain a negative electrode sheet. 2) Battery assembly and testing: The obtained negative electrode sheet was placed in a vacuum oven at a temperature of 100°C and a vacuum of -90kPa to dry. After drying for 5 hours, the negative electrode sheet was removed from the vacuum oven, and after the negative electrode plate was cooled, it was subjected to subsequent processing such as cutting, roll pressing, and die cutting. The negative and positive electrode sheets were then assembled together to form a button-type half cell, and an electrolyte solution with a LiPF6 concentration of 1.08 mol / kg was injected into the experimental battery. Initial capacity and efficiency tests were performed at 25°C, followed by a low-temperature capacity test at 10°C with a current of 0.5C, a discharge ratio performance test at a discharge current of 3C, and a room-temperature cycle performance test at a current of 1C. The experimental results are shown in Table 1.

[0061] Comparative Example 5 1) Preparation of negative electrode sheet: 93g of silicon-based material-containing graphite (negative electrode active material) and 1.5g of conductive agent Super-p were weighed and mixed uniformly, 2g of thickener carboxymethylcellulose (CMC) was added, deionized water was added and stirred for 15 minutes, then 1.116g of deionized aqueous solution / suspension containing sodium polyaspartate obtained below (negative electrode additive) was added, where the amount of sodium polyaspartate added was 0.279g (0.3wt% based on the total weight of active material), (wherein the content of sodium polyaspartate in the deionized aqueous solution / suspension of sodium polyaspartate was 25%, and the amount of insoluble matter of sodium polyaspartate in the aqueous solution / suspension was 40%) was kept stirring for 30 minutes, and finally 3.5g of adhesive styrene butadiene rubber (SBR) was added and stirred for 30 minutes to obtain negative electrode slurry. The obtained negative electrode slurry was allowed to stand for 1 hour, and then the obtained slurry was applied onto a copper foil and dried at 80° C. to obtain a negative electrode sheet. 2) Battery assembly and testing: The obtained negative electrode sheet was placed in a vacuum oven at a temperature of 100°C and a vacuum of -90kPa to dry. After drying for 5 hours, the negative electrode sheet was removed from the vacuum oven, and after the negative electrode plate was cooled, it was subjected to subsequent processing such as cutting, roll pressing, and die cutting. The negative and positive electrode sheets were then assembled together to form a button-type half cell, and an electrolyte solution with a LiPF6 concentration of 1.08 mol / kg was injected into the experimental battery. Initial capacity and efficiency tests were performed at 25°C, followed by a low-temperature capacity test at 10°C with a current of 0.5C, a discharge ratio performance test at a discharge current of 3C, and a room-temperature cycle performance test at a current of 1C. The experimental results are shown in Table 1.

[0062] Example 14: 1) Preparation of negative electrode sheet: 93g of silicon-based material-containing graphite (negative electrode active material) and 1.5g of conductive agent Super-p were weighed and mixed uniformly, 2g of thickener carboxymethylcellulose (CMC) was added, deionized water was added and stirred for 15 minutes, then 3.4875g of deionized aqueous solution / suspension containing sodium polyaspartate obtained below (negative electrode additive) was added, where the amount of sodium polyaspartate added was 1.395g (1.5wt% based on the total weight of active material), (wherein the content of sodium polyaspartate in the deionized aqueous solution / suspension of sodium polyaspartate was 40%, and the amount of insoluble matter of sodium polyaspartate in the aqueous solution / suspension was 1%) was continuously stirred for 30 minutes, and finally 3.5g of adhesive styrene butadiene rubber (SBR) was added and stirred for 30 minutes to obtain negative electrode slurry. The obtained negative electrode slurry was allowed to stand for 1 hour, and then the obtained slurry was applied onto a copper foil and dried at 80° C. to obtain a negative electrode sheet. 2) Battery assembly and testing: The obtained negative electrode sheet was placed in a vacuum oven at a temperature of 100°C and a vacuum of -90kPa to dry. After drying for 5 hours, the negative electrode sheet was removed from the vacuum oven, and after the negative electrode plate was cooled, it was subjected to subsequent processing such as cutting, roll pressing, and die cutting. The negative and positive electrode sheets were then assembled together to form a button-type half cell, and an electrolyte solution with a LiPF6 concentration of 1.08 mol / kg was injected into the experimental battery. Initial capacity and efficiency tests were performed at 25°C, followed by a low-temperature capacity test at 10°C with a current of 0.5C, a discharge ratio performance test at a discharge current of 3C, and a room-temperature cycle performance test at a current of 1C. The experimental results are shown in Table 1.

[0063] Example 15: 1) Preparation of negative electrode sheet: 93g of silicon-based material-containing graphite (negative electrode active material) and 1.5g of conductive agent Super-p were weighed and mixed uniformly, 2g of thickener carboxymethylcellulose (CMC) was added, deionized water was added and stirred for 15 minutes, then 5.8125g of deionized aqueous solution / suspension containing sodium polyaspartate obtained below (negative electrode additive) was added, where the amount of sodium polyaspartate added was 2.325g (2.5wt% based on the total weight of active material), (wherein the content of sodium polyaspartate in the deionized aqueous solution / suspension of sodium polyaspartate was 40%, and the amount of insoluble matter of sodium polyaspartate in the aqueous solution / suspension was 1%) was kept stirring for 30 minutes, and finally 3.5g of adhesive styrene butadiene rubber (SBR) was added and stirred for 30 minutes to obtain negative electrode slurry. The obtained negative electrode slurry was allowed to stand for 1 hour, and then the obtained slurry was applied onto a copper foil and dried at 80° C. to obtain a negative electrode sheet. 2) Battery assembly and testing: The obtained negative electrode sheet was placed in a vacuum oven at a temperature of 100°C and a vacuum of -90kPa to dry. After drying for 5 hours, the negative electrode sheet was removed from the vacuum oven, and after the negative electrode plate was cooled, it was subjected to subsequent processing such as cutting, roll pressing, and die cutting. The negative and positive electrode sheets were then assembled together to form a button-type half cell, and an electrolyte solution with a LiPF6 concentration of 1.08 mol / kg was injected into the experimental battery. Initial capacity and efficiency tests were performed at 25°C, followed by a low-temperature capacity test at 10°C with a current of 0.5C, a discharge ratio performance test at a discharge current of 3C, and a room-temperature cycle performance test at a current of 1C. The experimental results are shown in Table 1.

[0064] [Table 1]

[0065] As can be seen from Table 1 above, when polyaspartate is used as a lithium ion secondary battery negative electrode additive, an appropriate amount of polyaspartate is added to a deionized aqueous solution / suspension, the amount of insoluble matter of polyaspartate in the aqueous solution / suspension is appropriate, and a lithium ion secondary battery negative electrode slurry is prepared therewith, all of the lithium ion secondary batteries exhibit excellent electrochemical performance, and here, Examples 9 and 13 exhibit the most excellent electrochemical performance. From a comparison with Comparative Example 3, it can be seen that the results of the secondary batteries of Examples 7 to 10, in which polyaspartate is added as a lithium ion secondary battery negative electrode additive, are all superior to the results of Comparative Example 3 in terms of capacity retention, particularly at room temperature and low temperature.

[0066] In addition, in Comparative Example 4, an excess of sodium polyaspartate (5% based on the active material) was added as an additive for the negative electrode of the lithium ion secondary battery, which is higher than the range of 0.05 wt% to 3 wt% based on the total weight of the active material of sodium polyaspartate of the present invention, and therefore the electrochemical performance was disadvantageously degraded. The electrochemical performance of Comparative Example 4 was disadvantageously degraded compared to Comparative Example 3 (no polyaspartate was added) in terms of, for example, discharge capacity, charge / discharge efficiency, and capacity retention rate at room temperature and low temperature. In particular, the discharge magnification was only about half that of Example 13.

[0067] In addition, in the lithium ion secondary battery negative electrode additive of Comparative Example 5, the content of sodium polyaspartate in the deionized aqueous solution / suspension of sodium polyaspartate is 25%, which is lower than the content of sodium polyaspartate in the range of 40 wt% to 50 wt% of the present invention, and the amount of insoluble matter of sodium polyaspartate in the aqueous solution / suspension is 40%, which is higher than the range of less than 30 wt% of the present invention. Therefore, the lithium ion secondary battery of Comparative Example 5 shows a clear decrease in electrical performance compared to Example 13, and in particular, the discharge rate is only about half that of Example 13, and the electrical performance is clearly inferior to that of Comparative Example 3 in which no polyaspartate is added.

[0068] The above description is merely a preferred embodiment of the present invention, and does not limit the present invention. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention are all intended to be included in the protection scope of the present invention.

Claims

1. Polyaspartic acid salt and water, The content of the polyaspartate in the lithium ion secondary battery negative electrode additive is within a range of 40 wt % to 50 wt %, and the amount of insoluble matter of the polyaspartate in the lithium ion secondary battery negative electrode additive is less than 15 wt % based on the total weight of the lithium ion secondary battery negative electrode additive.

1. A lithium ion secondary battery negative electrode additive comprising:

2. The polyaspartate is selected from potassium polyaspartate, sodium polyaspartate, barium polyaspartate, or any combination thereof.

2. The negative electrode additive for a lithium ion secondary battery according to claim 1 .

3. The lithium ion secondary battery comprises the negative electrode additive according to claim 1 or 2, a negative electrode active material, and a conductive agent, Based on the total weight of the negative electrode active material, the amount of the polyaspartate in the lithium ion secondary battery negative electrode additive is within the range of 0.05 wt % to 3 wt %.

2. A lithium ion secondary battery negative electrode slurry comprising:

4. Further comprising an adhesive and a thickener.

4. The lithium ion secondary battery negative electrode slurry according to claim 3.

5. Based on the total weight of the negative electrode active material, the amount of the polyaspartate in the lithium ion secondary battery negative electrode additive is within the range of 0.05 wt % to 0.5 wt %.

4. The lithium ion secondary battery negative electrode slurry according to claim 3.

6. The negative electrode active material includes 85 parts by weight to 95 parts by weight of the negative electrode active material, 1 part by weight to 5 parts by weight of the adhesive, 1 part by weight to 5 parts by weight of the thickener, 1 part by weight to 5 parts by weight of the conductive agent, and a predetermined amount of the polyaspartic acid salt such that the amount of the polyaspartic acid salt is 0.05 wt % to 3 wt % of the total weight of the negative electrode active material.

5. The lithium ion secondary battery negative electrode slurry according to claim 4.

7. The negative electrode active material includes non-graphitizable carbon, graphitizable carbon, graphite, pyrolytic carbon, coke, glassy carbon, organic polymer sintered body, carbon fiber, activated carbon, and silicon-based material-containing graphite and silicon-based material; 4. The lithium ion secondary battery negative electrode slurry according to claim 3.

8. A lithium ion secondary battery including a positive electrode sheet, a negative electrode sheet, and a separator, A lithium ion secondary battery, comprising the lithium ion secondary battery negative electrode slurry according to any one of claims 3 to 7 applied onto the negative electrode sheet.

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