Anode materials for lithium ion battery cells
By adding lithiated sulfonated polymer to the silicon-based anode material, the volume change problem of silicon-based anode material during the charging and discharging process is solved, and a high capacity and high efficiency lithium-ion battery anode material is achieved, improving the cycle life.
Patent Information
- Application Number
- CN202380086241.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-12-16
- Filing Date
- 2023-12-15
- Publication Date
- 2025-07-25
AI Technical Summary
The silicon-based anode materials of existing lithium-ion batteries have volume expansion and contraction problems during charging and discharging, resulting in rapid reduction in capacity, and it is difficult for traditional Si-carbon composite materials to achieve high capacity and high efficiency.
Using a combination of silicon-based active material, conductive material and lithiated sulfonated polymer, a composite was formed by spray drying and heat treatment to prepare a silicon-based anode material containing 8 to 25 wt% lithiated sulfonated polymer to improve its conductivity and reversibility.
A silicon-based anode material with high capacity (1400mAh/g or greater) and high efficiency (65% or higher) is achieved, improving cycle life characteristics.
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Abstract
Description
Technical Field
[0001] The present disclosure relates to anode materials for lithium ion batteries. Background Art
[0002] Lithium ion batteries are currently the most widely used secondary battery systems in portable electronic communication devices, electric vehicles, and even in energy storage devices. Due to the advantages such as high energy density, operating voltage, and relatively low self-discharge rate compared to commercial aqueous secondary batteries such as Ni-Cd, Ni-MH, etc., such lithium ion batteries are the focus of attention. However, considering more efficient usage time in portable devices and improved energy characteristics in electric vehicles, improvement of electrochemical properties remains a technical problem to be solved. Therefore, a great deal of research and development is currently being carried out on the following four main raw materials: cathode, anode, electrolyte, and separator.
[0003] Among the raw materials, graphite-based materials that exhibit excellent capacity retention characteristics and efficiency can be commercially used for anodes. However, the relatively low theoretical capacity value (LiC6: 372 mAh / g) and low discharge capacity ratio of graphite-based materials may be somewhat insufficient to meet the high energy and high power density characteristics of the batteries required by the market.
[0004] Therefore, many researchers are interested in Group IV elements (Si, Ge, Sn) in the periodic table, and among them, Si has become a particularly attractive material due to its very high theoretical capacity (Li 15 Si4: 3600 mAh / g) and characteristics of low operating voltage (about 0.1 V for Li / Li+). However, since Si reacts with lithium during charging and discharging, significant volume expansion and contraction may occur, which may lead to pulverization of the silicon active material powder and poor electrical contact between the silicon active material powder and the current collector. This phenomenon causes the capacity of the lithium ion battery to rapidly decrease as the charge and discharge cycles proceed.
[0005] To overcome these problems, Patent Document 1 provides an anode material that exhibits improved cycle life characteristics at high capacity by including Si particles dispersed in SiO2 compared to the case of using Si alone. However, in addition to Si and SiO2, an intermediate phase called SiOx (0.5 ≤ x < 2) may be formed in the anode material, and some oxygen in SiOx may react with Li to form Li2O, a stable phase. Therefore, irreversible capacity may occur, which may lead to the problem that the cycle life characteristics of the anode material deteriorate.
[0006] To solve these problems, research has recently been actively conducted to improve reversibility by combining Si and carbon. However, Si-carbon composite anode materials have the following problems: the swelling problem of Si particles caused by repeated charging and discharging, which may prevent high capacity from being achieved.
[0007] (Prior art documents)
[0008] (Patent Document 1) Korean Patent Publication No. 10-2011-0029087 Summary of the Invention
[0009] Technical Problem
[0010] One aspect of the present disclosure aims to provide a silicon-based anode material having high capacity and high efficiency characteristics and a method for manufacturing the anode material.
[0011] Solution to the Problem
[0012] According to one aspect of the present disclosure, there is provided an anode material for a lithium-ion battery, comprising: a silicon-based active material; a conductive material; and 8 wt% to 25 wt% of a lithiated sulfonated polymer.
[0013] The silicon-based active material may be at least one selected from the group consisting of Si, SiOx (0.5 ≤ x < 2), and carbon composites thereof.
[0014] The conductive material may be CNT, graphene, or graphite.
[0015] The weight average molecular weight (Mw) of the lithiated sulfonated polymer may be 10,000 or more and 3,000,000 or less, and the lithiated sulfonated polymer may be Li-PSS.
[0016] The anode material may contain 40 wt% to 80 wt% of silicon (Si).
[0017] According to the FT-IR spectrum of the anode material, peaks at 830 cm -1 to 810 cm -1 due to the symmetric vibration of S-O and at 1075 cm -1 to 1055 cm -1 due to the symmetric vibration of S-O, and peaks at 1180 cm -1 to 1160 cm -1 and 1372 cm -1 to 1325 cm -1 due to the asymmetric and symmetric vibrations of Si=O can be observed.
[0018] The anode electrode comprising the above anode material can have a capacity of 1400 mAh / g or more and an initial efficiency of 65% or higher.
[0019] According to another aspect of the present disclosure, there is provided a method for manufacturing an anode material for a lithium-ion battery, the method comprising: preparing a silicon-based active material, a conductive material, and a lithiated sulfonated polymer; mixing the silicon-based active material, the conductive material, and the lithiated sulfonated polymer to produce a mixture; spray-drying the mixture to produce a composite; and heat-treating the composite produced by spray-drying at a temperature in the range of 200 °C to 300 °C. Additionally, the manufactured anode material may contain 8 wt% to 25 wt% of the lithiated sulfonated polymer.
[0020] The Si particles contained in the silicon-based active material can be manufactured by a dry grinding process, a wet grinding method such as bead milling or ball milling, a deposition method (thermal deposition, plasma deposition, etc.) performed in a vacuum environment, an electromagnetic melting method, or a co-evaporation method.
[0021] The wet grinding method can be performed using an organic solvent containing an aqueous solvent such as EtOH and IPA.
[0022] The Si particles contained in the silicon-based active material can have a median diameter of 30 nm to 500 nm.
[0023] The mixing of the silicon-based active material, the conductive material, and the lithiated sulfonated polymer can be performed using mechanical fusion, a VC, or a planetary mixer.
[0024] The anode material manufactured by the above manufacturing method may contain 40 wt% to 80 wt% of silicon (Si).
[0025] Advantages of the Invention
[0026] As described above, according to one aspect of the present disclosure, by adding a lithiated sulfonated polymer to a silicon-based anode material to compensate for the low electrical conductivity (10 -4 S / cm) of the Si raw material, a silicon-based anode material with high efficiency and high capacity and a method for manufacturing the silicon-based anode material can be provided. BRIEF DESCRIPTION OF THE DRAWINGS
[0027] Figure 1 is a conceptual diagram of the anode material according to the present disclosure. DETAILED DESCRIPTION
[0028] Hereinafter, preferred embodiments of the present disclosure will be described. However, the embodiments of the present disclosure can be modified in various forms, and the scope of the present disclosure should not be construed as being limited to the embodiments described below. In addition, the embodiments of the present disclosure are provided to those skilled in the art to further elaborate the present disclosure.
[0029] In this specification, unless otherwise specifically stated, the term "comprising" is used to indicate that other components can be included, rather than excluding other components.
[0030] In addition, unless otherwise specified, the unit % refers to wt%.
[0031] According to an embodiment of the present disclosure, the anode material may include: a silicon-based active material; a conductive material; and 8 wt% to 25 wt% of a lithiated sulfonated polymer.
[0032] That is, in an embodiment of the present disclosure, the target is a silicon-based anode material including a silicon-based active material. The silicon-based active material may be at least one selected from the group consisting of Si, SiOx (0.5 ≤ x < 2), and carbon composites thereof. The silicon-based active material may have the form of nanoparticles.
[0033] By including Si particles, compared with carbon-based anode materials, the silicon active material can achieve a high-capacity battery. In addition, in an embodiment of the present disclosure, the Si particles may be fine particles having a median diameter (D50) of 30 nm to 500 nm. The median diameter refers to the diameter at the center of the diameter distribution obtained when measured by a diameter analyzer from Beckmann Coulter. For surface stability, the Si particles may include a carbon coating.
[0034] As an example of the silicon active material, a Si-carbon composite may exist. The Si-carbon composite can be manufactured by coating a carbon material such as graphite on the Si particles, thereby preventing the Si particles from swelling and ensuring the conductivity of the anode material.
[0035] The anode material may further include a conductive material having excellent conductivity to improve the cycle efficiency during charging and discharging, and the conductive material may include CNT, graphene, or graphite.
[0036] The anode material may contain 8 wt% to 25 wt% of lithiated sulfonated polymer. The sulfonated polymer used as the ion exchange membrane of the fuel cell unit forms a solid-phase carrier, thereby allowing the silicon-based active material to be well formed on the carrier. In addition, by adding lithium ions to the sulfonated group, the reversibility of the anode material can be improved, thereby improving the low efficiency of the silicon-based anode material. When the content of the lithiated sulfonated polymer is less than 8 wt%, this effect may not be guaranteed, and the more preferred lower limit of the content of the lithiated sulfonated polymer is 12%, and its even more preferred lower limit is 14%. On the other hand, when the content of the lithiated sulfonated polymer exceeds 25 wt%, the content of Si particles and the conductive material may be relatively reduced, resulting in poor long-term life characteristics. More preferably, the content of the lithiated sulfonated polymer may be 23% or less.
[0037] The lithiated sulfonated polymer is not particularly limited within the range that can achieve the above object, and a copolymer containing a monomer having one or more lithiated sulfonated groups may also be included therein. In addition, the embodiments thereof are not limited thereto, but the lithiated sulfonated polymer may have a weight average molecular weight (Mw) of 10,000 or more and 3,000,000 or less. As an embodiment of the lithiated sulfonated polymer of the present disclosure, lithiated polystyrene sulfonate (Li-PSS) may be present.
[0038] According to an embodiment of the present disclosure, the anode material may include 40 wt% to 80 wt% of silicon (Si). When the content of Si is greater than 80 wt%, due to repeated charging and discharging, problems such as electrode swelling may occur, resulting in a problem of shortened cycle life. The more preferred upper limit of the content of Si is 70%, and the even more preferred upper limit of the content of Si is 65%. On the other hand, in order to provide a high-capacity silicon-based anode material, it is preferably included in an amount of 40 wt% or more. The more preferred lower limit of the content of Si is 45%, and the even more preferred lower limit of the content of Si is 60%.
[0039] Since the anode material contains lithiated sulfonated groups, according to the FT-IR spectrum of the present disclosure, peaks at 830 cm -1 to 810 cm -1 due to the symmetric vibration of S-O and peaks at 1075 cm -1 to 1055 cm -1 can be observed, as well as peaks at 1180 cm -1 to 1160 cm -1 and peaks at 1372 cm -1 to 1325 cm -1 due to the asymmetric vibration and symmetric vibration of S=O.
[0040] An anode electrode containing lithium ions with a silicon-based anode material according to the present disclosure exhibits high capacity and high efficiency characteristics. Preferably, an anode electrode containing lithium ions with the anode material according to the present disclosure can have a capacity of 1400 mAh / g or greater and an initial efficiency of 65% or higher.
[0041] Hereinafter, a method for manufacturing the anode material according to the present disclosure is described.
[0042] A method for manufacturing an anode material according to the present disclosure may include: preparing a silicon-based active material, a conductive material, and a lithiated sulfonated polymer; mixing the silicon-based active material, the conductive material, and the lithiated sulfonated polymer to produce a mixture; spray-drying the mixture to produce a composite; and heat-treating the composite produced by spray-drying at a temperature in the range of 200 °C to 300 °C. Additionally, the manufactured anode material may contain 8 wt% to 25 wt% of the lithiated sulfonated polymer.
[0043] Si particles contained in the silicon-based active material can be manufactured by a dry grinding process, a wet grinding method such as bead milling or ball milling, a deposition method (thermal deposition, plasma deposition, etc.) performed in a vacuum environment, an electromagnetic melting method, or a co-evaporation method. Preferably, a wet grinding method that can minimize the oxidation degree of Si particles and facilitate diameter control can be used.
[0044] The wet grinding method can be performed using an organic solvent containing an aqueous system, and as a preferred embodiment, EtOH and IPA can be used to prevent the oxidation of Si.
[0045] Additionally, the median diameter of Si particles contained in the silicon-based active material can be 30 nm to 500 nm. When the median diameter of Si particles exceeds 500 nm, the capacity may increase, but the life of the electrode may deteriorate due to the electrode swelling problem. A more preferred upper limit of the median diameter of Si particles is 250 nm, and an even more preferred upper limit of the median diameter of Si particles is 200 nm. On the other hand, when the median diameter of Si particles is less than 30 nm, there is a problem that the high capacity characteristics of the anode material may not be ensured. More preferably, the median diameter of Si particles can be 50 nm or greater.
[0046] As described above, the anode material may include a lithiated sulfonated polymer to form a solid-phase carrier while improving the reversibility of the anode material. Additionally, as a non-limiting example, the lithiated sulfonated polymer contained in the anode material may be Li-PSS. Li-PSS can be manufactured by the reaction of polystyrene sulfonic acid (PSSA) and LiOH. In this case, organic solvents such as dimethyl sulfoxide (DMSO) and tetrahydrofuran (THF) can be used as solvents for dissolving Li-PSS.
[0047] Thereafter, the silicon-based active material, the conductive material, and the lithiated sulfonated polymer can be mixed in the presence of a solvent, the mixture can be spray-dried to form a composite, and the solvent can be dried. In an embodiment of the present disclosure, the solvent can be the solvent used when pulverizing Si particles, but the embodiment is not necessarily limited thereto.
[0048] By mixing, the silicon-based active material, the conductive material, and the lithiated sulfonated polymer can be uniformly dispersed. The mixing method within the range capable of achieving the above object is not particularly limited, but as an embodiment, the mixing can be performed using mechanical fusion, VC, or a planetary mixer.
[0049] After spray drying, the resulting composite can be heat-treated at a temperature in the range of 200 °C to 300 °C. The heat treatment operation is performed to form the lithiated sulfonated polymer into a solid-phase carrier and to uniformly distribute the polymer between the Si particles. When the heat treatment is performed at a temperature lower than 200 °C, the above effects may not be achieved. On the other hand, when the heat treatment is performed at a temperature exceeding 300 °C, the charge / discharge capacity and efficiency may decrease due to side reactions of Si.
[0050] The silicon-based anode material manufactured by the above manufacturing method can contain 40 wt% to 80 wt% of silicon (Si).
[0051] Mode of the Invention
[0052] PSSA and LiOH are added to a DMSO solvent at a mass ratio of 1:5, reacted at 90 °C for 12 hours or longer, and precipitated Li-PSSA is obtained using THF. The precipitated Li-PSSA is washed with EtOH to obtain Li-PSS.
[0053] In this experiment, EtOH was used as the solvent, and nano-sized Si was obtained in a slurry state using a wet bead mill. The median diameter of the silicon particles was 100 nm. After mixing the slurry with CNT, the above Li-PSS was additionally added to prepare a uniform slurry. This mixing was performed by a mechanical fusion process. At this step, its solid content was about 9% to 10%. Then, the slurry was spray-dried to remove the solvent, and a composite of Si particles containing Li-PSS, precursor, and CNT was prepared. Thereafter, heat treatment was performed at a temperature in the range of 200 °C to 300 °C to obtain the final product. The composition ratios of Si, CNT, and Li-PSS of the obtained final product are shown in Table 2.
[0054] Figure 1 A conceptual diagram of the anode material according to the present disclosure is shown.
[0055] The characteristic peaks were observed using an FT-IR device to confirm whether Li-PSS and the carrier were generated after obtaining the active material, and the results are shown in Table 2. Peaks generated by the symmetric vibration of S-O can be observed in the region of 830 cm -1 to 810 cm -1 and from 1075 cm -1 to 1055 cm -1 , and peaks generated by the symmetric and asymmetric vibrations of Si=O can be observed in the region of 1180 cm -1 to 1160 cm -1 and from 1372 cm -1 to 1325 cm -1 .
[0056] To measure the electrochemical performance, the Si-carbon composite anode active material was coated on a Cu current collector with a loading of 5 mg / cm 2 and an electrode density of 1.2 g / cc to 1.3 g / cc, and then wound, and a CR-2032 type coin half-cell unit was fabricated, and a charge-discharge test was performed within an operating voltage range of 0.005 V to 1.0 V. The binder used for electrode fabrication was a polyacrylic acid (PAA) system, and the electrolyte was EC:DEC = 1:1 (1.0 M LiPF6) without additives. The current during charge-discharge was measured at 0.1 C in the initial cycle. The capacity and initial efficiency measured by this process are shown in Table 1.
[0057] [Table 1]
[0058]
[0059] [Table 2]
[0060] <![CDATA[FT-IR [S-O] Wavenumber (cm -1 )]]> <![CDATA[FT-IR [S=O] wavenumber (cm -1 )]]> Inventive Example 1 825，1068 1175，1325 Inventive Example 2 823，1068 1172，1348 Inventive Example 3 828，1071 1168，1353 Inventive Example 4 826，1072 1173，1356 Comparative Example 1 826，1075 1175，1359 Comparative Example 2 822，1067 1170，1350 Comparative Example 3 822，1067 1170，1350
[0061] In the case of Comparative Example 1 and Comparative Example 2 where the Li-PSS content exceeded 25%, the results showed lower capacity and initial efficiency. It was confirmed that this was because as the Li-PSS content increased, the content of the conductive material decreased and the binding force of the carrier decreased.
[0062] In the case of Comparative Example 3, the low conductivity of Si could not be compensated by containing less than 8 wt% of Li-PSS, resulting in a relatively low initial efficiency.
[0063] Meanwhile, in the case where the anode material did not contain Li-PSS at all, there was a problem that it was difficult to form a powder because the anode material had a structure without a carrier.
[0064] On the other hand, in Invention Examples 1 to 4, since the anodic battery contains 8 wt% to 25 wt% of lithiated sulfonated polymer, it can have high capacity and excellent initial efficiency characteristics.
[0065] In addition, referring to Table 2, regarding the FT-IR spectrum, in all examples of Invention Examples 1 to 4 and Experimental Examples 1 to 3, the peaks at 830 cm -1 to 810 cm -1 generated by the symmetric vibration of S-O, the peaks at 1075 cm -1 to 1055 cm -1 and the peaks at 1180 cm -1 to 1160 cm -1 generated by the asymmetric and symmetric vibrations of Si=O, and the peaks at 1372 cm -1 to 1325 cm -1 can be observed. Therefore, it can be confirmed that Li-PSS with lithiated sulfonated groups is generated in all samples.
Claims
1. An anode material for a lithium-ion battery cell, comprising: A silicon-based active material; A conductive material; And 8 wt% to 25 wt% of a lithiated sulfonated polymer.
2. The anode material for a lithium-ion battery cell according to claim 1, wherein, The silicon-based active material is at least one selected from the group consisting of Si, SiOx (0.5 ≤ x < 2), and carbon composites thereof.
3. The anode material for a lithium ion battery cell according to claim 1, wherein, The conductive material is CNT, graphene, or graphite.
4. The anode material for a lithium-ion battery cell according to claim 1, wherein, The lithiated sulfonated polymer has a weight-average molecular weight (Mw) of 10,000 or greater and 3,000,000 or less.
5. The anode material for a lithium-ion battery cell according to claim 1, wherein, The lithiated sulfonated polymer is Li-PSS.
6. The anode material for a lithium ion battery cell according to claims 1 to 5, wherein, Contains 40 wt% to 80 wt% of silicon (Si).
7. The anode material for a lithium ion battery cell according to claims 1 to 5, wherein, Based on the FT-IR spectrum of the anode material, peaks at 830 cm -1 to 810 cm -1 and at 1075 cm -1 to 1055 cm -1 were observed, as well as peaks at 1180 cm -1 to 1160 cm -1 and at 1372 cm -1 to 1325 cm -1 .
8. An anode electrode for a lithium-ion battery cell, comprising: The anode material according to claims 1 to 7.
9. The anode electrode for a lithium-ion battery cell according to claim 8, wherein, The anode electrode has a capacity of 1400 mAh / g or greater and an initial efficiency of 65% or higher.
10. A method for manufacturing an anode material for a lithium-ion battery cell, comprising: Preparing a silicon-based active material, a conductive material, and a lithiated sulfonated polymer; Mixing the silicon-based active material, the conductive material, and the lithiated sulfonated polymer to produce a mixture; Spray-drying the mixture to produce a composite; and Heat-treating the composite produced by spray-drying at a temperature in the range of 200 °C to 300 °C, Wherein the manufactured anode material contains 8 wt% to 25 wt% of a lithiated sulfonated polymer.
11. The method for manufacturing an anode material for a lithium-ion battery cell according to claim 10, wherein, The Si particles contained in the silicon-based active material are manufactured by a dry grinding process, a wet grinding method such as bead milling or ball milling, a deposition method (thermal deposition, plasma deposition, etc.) performed in a vacuum environment, an electromagnetic melting method, or a co-evaporation method.
12. The method for manufacturing an anode material for a lithium-ion battery cell according to claim 11, wherein, The wet grinding method is performed using an organic solvent containing an aqueous solvent such as EtOH and IPA.
13. The method for manufacturing an anode material for a lithium-ion battery cell according to claim 10, wherein, The Si particles contained in the silicon-based active material have a median diameter of 30 nm to 500 nm.
14. The method for manufacturing an anode material for a lithium ion battery cell according to claim 10, wherein, The mixing of the silicon-based active material, the conductive material, and the lithiated sulfonated polymer is performed using mechanical fusion, VC, or a planetary mixer.
15. The method for manufacturing an anode material for a lithium-ion battery cell according to claim 10, wherein, The manufactured anode material contains 40 wt% to 80 wt% of silicon (Si).