A lithium ion battery negative electrode material, a negative electrode and a preparation method thereof, and a lithium ion battery

Abstract

The present application relates to the technical field of battery, and provides a lithium ion battery negative electrode material, a negative electrode and a preparation method thereof, and a lithium ion battery.The lithium ion battery negative electrode material provided by the present application comprises secondary graphite, a modifier, a conductive agent and a binder; the modifier is graphene aerogel.The graphene aerogel is added into the negative electrode material as the modifier, the graphene aerogel is compatible with the existing commercial graphite negative electrode material base system in the lithium ion battery, and can quickly form a uniform and stable SEI layer after being mixed with the secondary graphite, so that the cycle life of the battery can be doubled without affecting the capacity of the battery; and the graphene aerogel has a large number of defects, which can promote Li + adsorption, greatly improve the lithium storage capacity and cycle life.Meanwhile, the negative electrode material provided by the present application is low in cost and is conducive to large-scale production.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a lithium ion battery negative electrode material, a negative electrode and a preparation method thereof, and a lithium ion battery. BACKGROUND

[0002] With the continuous development of new energy field, electrochemical energy storage and the development of clean, intelligent and green energy are attracting more and more attention, especially the fixed energy storage power station, which has stable and long-term power supply, is the key to meet the construction requirements of energy storage power station. However, the dendrite problem of lithium metal will cause irreversible damage to the battery and lead to poor cycle life. Although the electrolyte engineering is being developed at present, the cost, process and other problems make it still not ready for complete industrialization in the next few years.

[0003] The negative electrode material acts as a carrier of lithium ions and electrons in the battery, plays an important role in energy storage and release, and directly affects the energy density, cycle life, safety, fast charging ability and other performances of the battery. At present, the most widely used negative electrode material of lithium ion battery is secondary graphite, and the technology for improving the performance of lithium ion battery in the field mainly focuses on the surface modification of graphite. For example, the graphite is modified by metal / metal oxide coating, carbon doping and other ways to improve Li + transport kinetics and reduce the damage of lithium dendrite. However, these strategies are difficult to meet the fast diffusion kinetics in the graphite particles at the same time, and the surface modification of graphite may cause low initial efficiency, thereby affecting the battery capacity. +

[0004] In the related art, a silicon-based lithium supplement modification material is disclosed, which disperses the lithium-containing component on the surface or in the pores of the porous silicon matrix to realize high-content pre-lithium supplement and effectively improve the initial efficiency and cycle stability of the lithium ion battery. However, this method increases the lithium-containing component in the negative electrode material, and needs to disperse the lithium-containing component in the porous silicon matrix, which increases the overall production cost and the complexity of the production line.

[0005] In summary, there is an urgent need to develop a negative electrode material with simple composition that can effectively improve the cycle life of lithium ion battery. SUMMARY

[0006] Therefore, the present application provides a lithium ion battery negative electrode material, a negative electrode and a preparation method thereof, and a lithium ion battery. The graphene aerogel is added as a modifier into the negative electrode material, and after mixing with the secondary graphite, a uniform and stable SEI layer can be quickly formed, which can double the cycle life of the battery without affecting the battery capacity.

[0007] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0008] ​A lithium ion battery negative electrode material comprises the following components: secondary graphite, a modifier, a conductive agent and a binder; the modifier is graphene aerogel; the mass ratio of the secondary graphite and the graphene aerogel is 9.5:0.5-0.5:9.5.

[0009] Preferably, the I D / I G value of the graphene aerogel is 0.8-1.3.

[0010] Preferably, the average particle size of the graphene aerogel is 4-10 μm, the average pore size is 1-30 nm, the BET specific surface area is 1-2000 m 2 g -1 , and the pore volume is 0.001-2 m 2 g -1 .

[0011] Preferably, the weight ratio of the graphene aerogel and the secondary graphite is 0.5-3:7-9.5.

[0012] Preferably, the mass ratio of the total weight of the secondary graphite and the graphene aerogel to the conductive agent and the binder is 6-8:1-3:1.

[0013] Preferably, the conductive agent is acetylene black; and the binder is polyvinylidene fluoride and / or polyimide.

[0014] The application further provides a lithium ion battery negative electrode comprising a current collector and a negative electrode material arranged on the surface of the current collector; the negative electrode material is the lithium ion battery negative electrode material described in the above-mentioned scheme.

[0015] The application further provides a preparation method of the lithium ion battery negative electrode described in the above-mentioned scheme, comprising the following steps:

[0016] Mixing the lithium ion battery negative electrode material and a solvent to obtain a negative electrode slurry;

[0017] Drying the negative electrode slurry after coating on the surface of a current collector to obtain the lithium ion battery negative electrode.

[0018] Preferably, the coating method is doctor blading, the doctor blading rate is 3-8 cm / s -1 , and the doctor blading thickness is 500-1000 μm.

[0019] The application further provides a lithium ion battery comprising a positive electrode, a negative electrode, a separator and an electrolyte; the negative electrode is the lithium ion battery negative electrode described in the above-mentioned scheme or the lithium ion battery negative electrode prepared by the preparation method described in the above-mentioned scheme.

[0020] This invention provides a lithium-ion battery anode material, comprising the following components: secondary graphite, a modifier, a conductive agent, and a binder; the modifier is graphene aerogel; the mass ratio of secondary graphite to graphene aerogel is 9.5:0.5 to 0.5:9.5. Graphene aerogel is a type of graphite, compatible with existing commercial graphite anode material substrate systems in lithium-ion batteries, does not affect electrode capacity, and can be directly used in existing lithium-ion battery material systems; graphene aerogel has numerous edge and lamellar lattice defects, which can promote Li-ion... + Adsorption significantly improves lithium storage capacity and cycle life.

[0021] Furthermore, graphene aerogel, as a modifier, can be mixed with secondary graphite to quickly form a uniform and stable SEI layer and construct a stable negative electrode. The main principles are as follows: (1) Increase active sites: Defects in graphene aerogel can provide more active sites, which can promote the decomposition of substances in the electrolyte, thereby accelerating the formation of the SEI layer; (2) Improve ion transport: The presence of defects can increase the specific surface area and porosity of the material, which helps to improve the transport path of lithium ions, enabling lithium ions to pass through the SEI layer more quickly, thereby accelerating the formation of the SEI layer; (3) Promote uniform film formation: Defects in graphene aerogel can promote the uniform distribution of additives in the electrolyte, which helps to form a uniform and stable SEI layer and improve the cycle stability and safety of the battery.

[0022] Furthermore, the negative electrode material provided by this invention is inexpensive, which is conducive to large-scale production. Attached Figure Description

[0023] Figure 1 These are scanning electron microscope images of the graphene aerogel used in the embodiments of the present invention;

[0024] Figure 2 The Raman curves of the graphene aerogel used in the embodiments of the present invention are shown below.

[0025] Figure 3 The cyclic voltammetry curves of the graphene aerogel used in the embodiments of the present invention are shown below.

[0026] Figure 4 A scanning electron microscope image of the negative electrode surface of the lithium-ion battery with graphene aerogel added in Example 1 after 15 cycles at a current density of 1C.

[0027] Figure 5 The charge-discharge curve of the lithium-ion battery with graphene aerogel added in Example 1 after 200 cycles at a current density of 1C.

[0028] Figure 6 A scanning electron microscope image of the negative electrode surface of the lithium-ion battery with graphene aerogel added in Example 1 after 200 cycles at a current density of 1C.

[0029] Figure 7 The cycle life curve of the lithium ion battery added with graphene aerogel in Example 1 is compared with that of a commercial secondary graphite lithium ion battery at a 1C current density;

[0030] Figure 8 The cycle life curve of the lithium ion battery added with graphene aerogel in Example 2 is compared with that of a commercial secondary graphite lithium ion battery at a 1C current density. DETAILED DESCRIPTION

[0031] The present application provides a lithium ion battery negative electrode material, comprising the following components: secondary graphite, graphene aerogel, conductive agent and binder; the mass ratio of the secondary graphite and graphene aerogel is 9.5:0.5-0.5:9.5.

[0032] In the present application, the secondary graphite is a commercial secondary graphite, and the present application does not have special requirements for the source of the secondary graphite, and a commercially available product can be used.

[0033] In the present application, the weight ratio of the graphene aerogel and secondary graphite is preferably 0.5-3:7-9.5, and can be specifically 0.5:9.5, 1:9, 1.5:8.5, 2:8 or 3:7, and is further preferably 1:9 or 2:8.

[0034] In the present application, the I D / I G value of the graphene aerogel is preferably 1.08; the average particle size of the graphene aerogel is preferably 4-10 μm, and can be specifically 5 μm, 8 μm or 9.84 μm; the average pore size is preferably 1-30 nm, and can be specifically 1 nm, 1.736 nm, 2 nm, 5 nm, 10 nm or 25 nm; the BET specific surface area is preferably 1-2000 m 2 g -1 , and can be specifically 500 m 2 g -1 , 1000 m 2 g -1 , 1500 m 2 g -1 or 2000 m 2 g -1 ; the pore volume is preferably 0.001-2 m 2 g -1 , and can be specifically 0.1 m 2 g -1 , 0.5 m 2 g -1 , 0.682 m 2 g -1 , 1 m 2g -1 or 1.5 m 2 g -1 The graphene aerogel of the present application has no special requirements on its source, and can be commercially available or prepared by methods well known to those skilled in the art, as long as the average particle size, average pore size, BET specific surface area and pore volume meet the above requirements.

[0035] In the present application, the mass ratio of the total weight of the secondary graphite and graphene aerogel to the conductive agent and the binder is preferably 6-8:1-3:1, and can be specifically 7:2:1, 8:1:1 or 6:3:1; the conductive agent is preferably acetylene black; and the binder is preferably polyvinylidene fluoride (PVDF) and / or polyimide.

[0036] The present application also provides a lithium ion battery negative electrode, comprising a current collector and a negative electrode material arranged on the surface of the current collector; the negative electrode material is the lithium ion battery negative electrode material described in the above scheme.

[0037] The present application also provides a preparation method of the lithium ion battery negative electrode described in the above scheme, comprising the following steps:

[0038] mixing the lithium ion battery negative electrode material and the solvent to obtain a negative electrode slurry;

[0039] drying the negative electrode slurry after coating on the surface of the current collector to obtain the lithium ion battery negative electrode.

[0040] In the present application, the solvent is preferably N-methyl pyrrolidone; and the mixing of the lithium ion battery negative electrode material and the solvent preferably comprises: mixing the secondary graphite, the graphene aerogel and the conductive agent to obtain a mixed powder; mixing the binder and the solvent to obtain a binder solution; and mixing the mixed powder and the binder solution to obtain the negative electrode slurry; the mixing of the secondary graphite, the graphene aerogel and the conductive agent is preferably solid-phase homogenization; the device used for the solid-phase homogenization is preferably a ball mill, a sand mill or a disperser; the mixing time is preferably 1-5 h, and more preferably 1-3 h; the mass ratio of the binder to the solvent is preferably 0.25-0.5:4.75-9.5, and the mixing time of the binder and the solvent is preferably 1-3 h; and the mixing time of the mixed powder and the binder solution is preferably 12-48 h.

[0041] After obtaining the negative electrode slurry, the present application coats the negative electrode slurry on the surface of the current collector and then dries to obtain the lithium ion battery negative electrode. In the present application, the current collector is preferably a copper foil; the coating method is preferably blade coating, and the blade coating rate is preferably 3-8 cm s -1 , and can be specifically 5 cm s -1or 6 cm s -1 ; the thickness of the doctoring is preferably 500-1000 μm; the drying is preferably carried out by air drying and vacuum drying in sequence; the temperature of the air drying is preferably 60-90℃, and the drying time is preferably 10-30 min; the temperature of the vacuum drying is preferably 60-90℃, and the drying time is preferably 12-24 h.

[0042] The application further provides a lithium ion battery comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the negative electrode is the lithium ion battery negative electrode described in the above-mentioned scheme or prepared by the preparation method described in the above-mentioned scheme; the application does not have special requirements for the positive electrode, the separator and the electrolyte, and any one known to those skilled in the art can be used.

[0043] The technical solutions in the application will be clearly and completely described below with reference to the embodiments in the application. Obviously, the described embodiments are only some of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the application.

[0044] The graphene aerogel used in the following examples has an average particle size of 9.84 μm, an average pore size of 1.736 nm, a BET specific surface area of 1572 m 2 g -1 , and a pore volume of 0.682 mLg -1 .

[0045] Example 1

[0046] (1) 3.6 g of commercial secondary graphite, 0.4 g of graphene aerogel and 1.14 g of acetylene black are uniformly mixed by a solid-phase homogenization reaction method, and the mixing time is 2 h to obtain a mixed powder.

[0047] (2) 1 g of PVDF powder is dissolved in 19 g of N-methyl pyrrolidone, stirred for 2 h at a speed of 1000 r / min to obtain a PVDF solution.

[0048] (3) 5.14 g of the mixed powder is uniformly stirred and mixed with 11.4 g of the PVDF solution, and the stirring time is 24 h to obtain a negative electrode slurry.

[0049] (4) taking 5 mL of the negative electrode slurry with a 1000 μm doctor blade, coating is completed at a speed of 5 cm s -1 , and then the coated copper foil is placed in a 90℃ air drying oven for rapid drying for 20 min, and then transferred into a 90℃ vacuum drying oven for drying for 12 h to obtain a negative electrode.

[0050] Performance test:

[0051] Figure 1 SEM image of graphene aerogel, Figure 2 Raman curve of graphene aerogel. According to Figures 1-2 It can be seen that the graphene aerogel has a porous structure, and the Raman curve shows that the graphene aerogel has a I D / I G The value is 1.08, indicating that there are a large number of defects, and the existence of defects can increase the specific surface area and porosity of the material, which helps to improve the transmission path of lithium ions, so that lithium ions can pass through the SEI layer more quickly, thereby accelerating the formation of the SEI layer.

[0052] Figure 3 Cyclic voltammetry curve of graphene aerogel. According to Figure 3 It can be seen that there is no obvious current mutation in the CV curve during the potential scanning process, indicating that the graphene aerogel has good electrochemical stability.

[0053] The lithium ion battery assembled with the negative electrode prepared in Example 1 was subjected to cyclic charge-discharge test, wherein lithium sheet was used as the positive electrode, and the electrolyte was LB-1178 (1M LiPF6, DMC:EC=7:3 Vol%, 5% FEC).

[0054] Figure 4 SEM image of the surface of the negative electrode of the lithium ion battery added with graphene aerogel after 15 cycles at a current density of 1C. According to Figure 4 It can be seen that after only 15 cycles, the negative electrode surface can exhibit a dense morphology, which is beneficial to improve the cycle stability of the electrode.

[0055] Figure 5 Charge-discharge curve of the lithium ion battery added with graphene aerogel at the 200th cycle at a current density of 1C. According to Figure 5 It can be seen that the electrode surface exhibits a dense, smooth and flat morphology, which is beneficial to improve the chemical cycle stability of the battery.

[0056] Figure 6 SEM image of the surface of the negative electrode of the lithium ion battery added with graphene aerogel after 200 cycles at a current density of 1C. According to Figure 6 It can be seen that the negative electrode surface after 200 cycles is more flat and regular, which is beneficial to the more uniform storage of lithium.

[0057] Figure 7 Cycle life curve of the lithium ion battery added with graphene aerogel in Example 1 compared with the commercial secondary graphite lithium ion battery at a current density of 1C. According to Figure 7 It can be seen that the capacity of the lithium ion battery assembled with the negative electrode added with graphene aerogel can reach 365mAh g -1Meanwhile, compared with the commercial secondary graphite lithium ion battery, the cycle life can be doubled.

[0058] Example 2

[0059] (1) Take 3.2 g of commercial secondary graphite, 0.8 g of graphene aerogel and 1.14 g of acetylene black, mix them uniformly by solid-phase homogenization reaction method, and mix for 2 h to obtain a mixed powder.

[0060] (2) Dissolve 1 g of PVDF powder in 19 g of N-methyl pyrrolidone, stir for 2 h at a speed of 1000 r / min to obtain a PVDF solution.

[0061] (3) Uniformly stir and mix 5.14 g of the mixed powder with 11.4 g of the PVDF solution, and stir for 24 h to obtain a negative electrode slurry.

[0062] (4) Take 5 mL of the negative electrode slurry with a 1000 μm doctor blade, complete coating at a speed of 5 cm / s with a copper foil as a substrate, and place it in a 90°C air drying oven for rapid drying for 20 min, and then transfer it into a 90°C vacuum drying oven for drying for 12 h to obtain a negative electrode. -1

[0063] The lithium ion battery assembled with the negative electrode prepared in Example 2 was subjected to cycle charge-discharge test, wherein the graphite electrode was used as a negative electrode, lithium sheet was used as a positive electrode, and the electrolyte composition was LB-1178.

[0064] Figure 8 The cycle life curve of the lithium ion battery with the graphene aerogel added in Example 2 compared with the commercial secondary graphite lithium ion battery at a current density of 1C was shown in FIG. 2. Figure 8 It can be seen that the capacity of the lithium ion battery assembled with the negative electrode with the graphene aerogel added in Example 2 can be stabilized at 345 mAh g -1 , and the cycle life can be doubled compared with the commercial secondary graphite lithium ion battery.

[0065] Comparative Example 1

[0066] (1) Take 3.6 g of commercial secondary graphite, 0.4 g of graphene powder and 1.14 g of acetylene black, mix them uniformly by solid-phase homogenization reaction method, and mix for 2 h to obtain a mixed powder. The graphene powder is prepared by liquid phase exfoliation method, and the Raman test shows that the I D :I G value is 0.25, the sheet crystal lattice is complete, the defects are few, the average particle size is 3.65 μm, and the specific surface area is 547 m 2 / g.

[0067] ​(2) 1 g PVDF powder was dissolved in 19 g N-methyl pyrrolidone, stirred for 2 h at 1000 r / min, to obtain a PVDF solution.

[0068] (3) 5.14 g mixed powder was uniformly mixed with 11.4 g PVDF solution by stirring for 24 h, to obtain a negative electrode slurry.

[0069] (4) A copper foil was used as a substrate, a 1000 μm doctor blade was used to take 5 mL of the negative electrode slurry, and coating was completed at a speed of 5 cm / s, and the coated copper foil was placed in a 90 °C air drying oven for rapid drying for 20 min, and then transferred to a 90 °C vacuum drying oven for drying for 12 h, to obtain a negative electrode. -1

[0070] The lithium ion battery assembled with the negative electrode prepared in Comparative Example 1 was subjected to cyclic charge-discharge test, in which lithium foil was used as a positive electrode, and electrolyte was LB-1178 (1M LiPF6, DMC:EC=7:3 Vol%, 5% FEC). The experimental results show that, compared with a commercial secondary graphite lithium ion battery, the cycle life of the lithium ion battery assembled with Comparative Example 1 can be improved by 37% at a current density of 1C, and the effect is lower than that of the lithium ion battery assembled with the negative electrode added with graphene aerogel, indicating that the large amount of defects in the graphene aerogel can more effectively improve the cycle life of the lithium ion battery.

[0071] The above only describes the preferred embodiments of the present application, and it should be noted that, for those skilled in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.​

Claims

1. A lithium-ion battery anode material, characterized in that, It comprises the following components: secondary graphite, modifier, conductive agent, and binder; the modifier is graphene aerogel; the mass ratio of secondary graphite to graphene aerogel is 8~9:1~2; the I content of the graphene aerogel is... D / I G The value is 1.08~1.3; the average particle size of the graphene aerogel is 9.84~10 μm, the average pore size is 1.736~2 nm, and the BET specific surface area is 1500~2000 m². 2 g -1 The pore volume is 0.682~2 m³. 2 g -1 .

2. The lithium-ion battery anode material of claim 1, wherein, The mass ratio of the total weight of the secondary graphite and graphene aerogel, the conductive agent and the binder is 6-8:1-3:

1.

3. The lithium-ion battery anode material of claim 1, wherein, The conductive agent is acetylene black; and the binder is polyvinylidene fluoride and / or polyimide.

4. A lithium-ion battery anode, characterized by, The lithium ion battery negative electrode comprises a current collector and a negative electrode material arranged on the surface of the current collector; the negative electrode material is the lithium ion battery negative electrode material according to any one of claims 1-3.

5. The method for preparing the lithium-ion battery negative electrode according to claim 4, characterized in that, The method comprises the following steps: Mixing the lithium ion battery negative electrode material and a solvent to obtain a negative electrode slurry; Drying the negative electrode slurry after coating on the surface of the current collector to obtain the lithium ion battery negative electrode.

6. The preparation method according to claim 5, characterized in that, The coating is performed by means of a doctor blade at a rate of 3 to 8 cm s -1 and a thickness of 500 to 1000 μm.

7. A lithium ion battery comprising a positive electrode, a negative electrode, a separator and an electrolyte, characterized in that, The negative electrode is the lithium ion battery negative electrode according to claim 4 or the lithium ion battery negative electrode prepared by the preparation method according to any one of claims 5-6.

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