Anode material for lithium-ion batteries, anode for lithium-ion batteries, and lithium-ion batteries
By using SiO particles with controlled trace elements in the negative electrode active material layer, the lithium-ion battery addresses cycle deterioration issues, enhancing conductivity and maintaining performance stability.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- ALMEDIO
- Filing Date
- 2024-11-19
- Publication Date
- 2026-05-29
AI Technical Summary
Lithium-ion secondary batteries using silicon-based materials for the negative electrode active material layer face rapid cycle deterioration due to repeated volume changes during lithium ion occlusion and release, leading to a decrease in charge and discharge performance.
Incorporating SiO particles with trace elements from specific groups (K, Na, Li, etc.) into the negative electrode active material layer, ensuring a total content of these elements is limited to suppress conductivity improvement and uniform lithium intercalation, thereby mitigating structural changes and electrolyte deterioration.
The solution effectively suppresses the degradation of charge and discharge performance by enhancing conductivity and ensuring uniform lithium intercalation, maintaining battery capacity and efficiency over multiple cycles.
Smart Images
Figure 2026088828000001
Abstract
Description
Technical Field
[0001] The disclosed embodiments relate to a negative electrode material for a lithium ion battery, a negative electrode for a lithium ion battery, and a lithium ion battery.
Background Art
[0002] Conventionally, a lithium ion secondary battery in which lithium ions contained in an electrolytic solution move between a positive electrode and a negative electrode is known. A lithium ion secondary battery is a lithium ion battery provided with a negative electrode active material layer that occludes lithium ions during charging and releases lithium ions during discharging.
[0003] As the negative electrode active material layer, a material applying a carbon-based material such as graphite is widely adopted. In recent years, in order to further increase the battery capacity, a lithium ion secondary battery provided with a negative electrode active material layer using a silicon-based material having a higher lithium ion occlusion ability than graphite alone or in combination has been studied (see, for example, Patent Document 1 and Patent Document 2).
Prior Art Documents
Patent Documents
[0004]
Patent Document 1
Patent Document 2
Summary of the Invention
Problems to be Solved by the Invention
[0005] However, in a lithium ion secondary battery applying a silicon-based material to a negative electrode active material layer, there has been a concern that cycle deterioration in which charge / discharge performance deteriorates easily occurs due to repeated volume changes accompanying lithium ion occlusion and release.
[0006] One embodiment has been made in view of the above, and aims to provide a negative electrode material for lithium-ion batteries, a negative electrode for lithium-ion batteries, and a lithium-ion battery that can suppress a decrease in charge and discharge performance. [Means for solving the problem]
[0007] A negative electrode material for a lithium-ion battery according to one embodiment includes SiO particles. The SiO particles contain one or more trace elements selected from the alkali metal element group consisting of K, Na, and Li. The total content of the said element group is 23 mg / kg or less. [Effects of the Invention]
[0008] According to one embodiment of the negative electrode material for lithium-ion batteries, the negative electrode for lithium-ion batteries, and the lithium-ion battery, the deterioration of charge and discharge performance can be suppressed. [Modes for carrying out the invention]
[0009] The embodiments of the lithium-ion battery negative electrode material, lithium-ion battery negative electrode, and lithium-ion battery disclosed herein will be described in detail below. However, the invention is not limited to the embodiments described below.
[0010] First, the configuration of the lithium-ion battery according to this embodiment will be described. In the following, a lithium-ion secondary battery will be used as an example of a lithium-ion battery.
[0011] A lithium-ion secondary battery (hereinafter also referred to as a "lithium secondary battery") comprises a positive electrode for lithium-ion secondary batteries (hereinafter also referred to as a "positive electrode"), a negative electrode for lithium-ion secondary batteries (hereinafter also referred to as a "negative electrode"), a separator, an insulating material, and an electrolyte.
[0012] The positive electrode comprises a positive electrode current collector and a positive electrode active material layer. The positive electrode current collector is electrically connected to a positive electrode can that also serves as the positive electrode terminal. For example, aluminum can be used as the positive electrode current collector.
[0013] Furthermore, as the positive electrode active material layer, for example, lithium cobalt composite oxide, lithium manganese composite oxide, lithium nickel composite oxide, lithium nickel cobalt composite oxide, lithium vanadium composite oxide, etc. may be used. In addition, the positive electrode active material layer may contain conductive additives or other additives as needed.
[0014] The negative electrode comprises a negative electrode current collector (hereinafter also referred to as the "current collector") and a negative electrode active material layer (hereinafter also referred to as the "active material layer") arranged on the current collector. The negative electrode is an electrode with a lower potential than the positive electrode.
[0015] For the current collector, for example, copper, nickel, titanium, stainless steel, etc., can be used.
[0016] The active material layer contains SiO particles containing the negative electrode active material. The SiO particles contain one or more trace elements selected from the alkali metal element group consisting of K, Na, and Li. The total content of these elements in the SiO particles is 23 mg / kg or less. The reason why the inclusion of SiO particles containing specific trace elements in the active material layer can suppress the degradation of charge and discharge performance is presumed to be as follows:
[0017] In other words, by incorporating the aforementioned trace elements into high-purity SiO, which has low conductivity and cannot be used as an electrode material on its own, conductivity is imparted to the SiO particles themselves, making them usable as a negative electrode material. Furthermore, the improved conductivity suppresses localized intercalation and release of lithium in the active material layer containing the SiO particles, enabling uniform intercalation and release of lithium throughout the entire SiO particle system. This suppresses cycle degradation associated with changes in the structure of the active material layer due to repeated intercalation and release of lithium ions.
[0018] Here, when the SiO particles contain one or more trace elements selected from the group of alkaline earth metal elements consisting of Mg, Ca, Sr, and Ba as trace elements, it is preferably 3 mg / kg or less, more preferably 0.5 mg / kg or more and 1 mg / kg or less. If it exceeds 3 mg / kg, there is a concern that these elements dissolve as impurities in the electrolyte and accelerate the deterioration of the electrolyte.
[0019] Also, when the SiO particles contain one or more trace elements selected from the group of Group 4 transition elements consisting of Ti, Zr, and Hf as trace elements, it is preferably 2 mg / kg or less, more preferably 0.5 mg / kg or more and 1 mg / kg or less. If the content of the metal elements of these Group 4 transition elements exceeds 2 mg / kg, there is a concern that these metal elements dissolve as impurities in the electrolyte and accelerate the deterioration of the electrolyte.
[0020] Also, when the SiO particles contain one or more trace elements selected from the group of Group 6 transition elements consisting of Cr, Mo, and W as trace elements, it is preferably 7 mg / kg or less, more preferably 1 mg / kg or more and 5 mg / kg. If the content of the metal elements of Group 6 transition elements exceeds 7 mg / kg, there is a concern that these metal elements dissolve as impurities in the electrolyte and accelerate the deterioration of the electrolyte.
[0021] Also, the SiO particles preferably contain 99.95% by mass or more, more preferably 99.97% by mass or more and 99.99% by mass or less of SiO. If the content of SiO is less than 99.95% by mass, the battery capacity of the lithium secondary battery 1 may not be sufficiently obtained.
[0022] Also, preferably 95% by volume or more, more preferably 97% by volume or more and 99.9% by volume or less of the SiO particles have a diameter of 0.12 μm or more and 0.90 μm or less. By having 95% by volume or more of the SiO particles with a diameter of 0.12 μm or more and 0.90 μm or less, the lithium ions can be appropriately occluded and released according to charge and discharge.
[0023] Also, the average particle diameter of the SiO particles can be, for example, 0.5 μm or more and 0.6 μm or less. Further, the thickness of the active material layer can be, for example, 150 μm or less, more preferably 1 μm or more and 120 μm or less. However, the average particle diameter of the SiO particles and the thickness of the active material layer are not limited thereto, and can be appropriately changed according to, for example, the desired performance and shape of the lithium secondary battery 1.
[0024] In addition to the trace elements described above, the SiO particles may contain one or more elements selected from other transition element groups consisting of Mn, Fe, Co, Ni, Cu, Al, S, and P. In such a case, the content of the metal elements in the other transition element groups is preferably 47 mg / kg or less, more preferably 5 mg / kg or more and 25 mg / kg or less. However, if the content of the metal elements in the other transition element groups exceeds 47 mg / kg, there is a concern that these will dissolve as impurities in the electrolyte and accelerate the deterioration of the electrolyte. Among the element groups described above as trace elements, nickel is particularly preferable because it has high reactivity and affinity with lithium and promotes the adsorption of lithium to the active material.
[0025] The active material layer may further contain a binder, a dispersant, and carbon particles or other conductive aids for imparting conductivity.
[0026] Examples of the binder include sodium alginate, polyglutamic acid, and polyacrylic acid. Examples of the dispersant include carboxymethyl cellulose (CMC). Examples of the conductive aids include acetylene black and carbon nanotubes.
[0027] The particle diameter and content of the SiO particles contained in the active material layer are measured based on a SEM (Scanning Electron Microscope) image of the active material layer cut in the thickness direction.
[0028] Furthermore, the content of various trace elements contained in the SiO particles within the active material layer is measured by preparing SiO particles or the active material layer as a sample and performing elemental analysis using methods such as X-ray fluorescence analysis, wavelength-dispersive X-ray spectroscopy (WDS), glow discharge mass spectrometry (GDMS), inductively coupled plasma (ICP), emission spectroscopy (ICP-AES), and ICP-MS.
[0029] A separator is placed between the positive and negative electrodes, separating them. Examples of separators include nonwoven fabrics made of organic or inorganic resin fibers, porous materials made of ceramics, polyethylene, polypropylene, and other polyolefins.
[0030] The insulating material is placed between the positive electrode canister and the negative electrode canister to prevent short circuits between them and to prevent leakage of the electrolyte sealed inside. As the insulating material, an insulating material with electrolyte resistance can be used, such as polypropylene or a fluorine-based material such as fluororesin or fluororubber.
[0031] The electrolyte is a non-aqueous electrolyte containing an organic solvent and a lithium salt, which is a lithium ion source. The organic solvent is preferably one with a high dielectric constant, low viscosity, and low vapor pressure. Examples of such organic solvents include one or more selected from ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, sulfolane, 1,2-dimethoxyethane, 1,3-dimethoxypropane, dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, methyl ethyl carbonate, dimethyl carbonate, and diethyl carbonate. Furthermore, the electrolyte is particularly preferable from the viewpoint of improving cycle characteristics if it contains either or both of ethylene carbonate and fluoroethylene carbonate as the organic solvent.
[0032] Furthermore, examples of lithium salts that can be used include LiClO4, LiBF4, LiPF6, LiCF3SO3, LiN(CF3SO2)2, and LiN(C2F5SO2)2. The electrolyte may also contain additives for purposes such as preventing overcharging and providing flame retardancy, as needed.
[0033] Furthermore, the electrolyte may be a fluid electrolyte, for example, a gel electrolyte obtained by gelling with a polymer to reduce its fluidity.
[0034] The shape of the lithium secondary battery may be any shape depending on the application, such as rectangular, cylindrical, button-shaped, coin-shaped, or flat. Furthermore, instead of a positive electrode casing and a negative electrode casing, a lithium secondary battery may use an insulating container equipped with positive and negative electrode terminals. Moreover, the electrode structure of the lithium secondary battery is not limited to a single-layer structure having a pair of positive and negative electrodes, but may also be a laminated structure having multiple positive and negative electrodes.
[0035] Although embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications are possible without departing from the spirit of the invention.
[0036] For example, the types of lithium-ion batteries are not limited to the lithium secondary batteries mentioned above. They may also include sulfur batteries (silicon-sulfur batteries), next-generation lithium batteries (all-solid-state lithium secondary batteries, lithium secondary batteries using high-capacity cathode materials, etc.), sodium secondary batteries, and other batteries with different electrode and electrolyte configurations. In other words, SiO particles can be used not only as a negative electrode material for the active material layer of lithium secondary batteries, but also as a negative electrode material for various lithium-ion batteries. [Examples]
[0037] (Example 1) [Preparation of negative electrode coating solution] 71 parts by mass of SiO powder (corresponding to "SiO particles", average particle size 0.5 μm, purity 99.95% by mass), 14.9 parts by mass of conductive additive (acetylene black), 0.1 parts by mass of conductive additive (CNT), 10 parts by mass of binder (sodium alginate:polyglutamic acid:polyacrylic acid = 1:1:1 (by mass%)), and 4 parts by mass of dispersant (CMC) were mixed and stirred with a solvent (water) to prepare a negative electrode coating solution with a solid content of 30%.
[0038] [Fabrication of negative electrode sheet] A negative electrode coating solution was applied to a 60mm x 40mm x 30μm copper foil (corresponding to the "current collector") to prepare an active material layer measuring 50mm x 40mm x 30μm.
[0039] [Preparation of cells (half-cells) for charge / discharge testing] Two sets of half-cells were prepared by sequentially stacking the negative electrode, separator, and counter electrode prepared as described above. These were connected in series and housed in an aluminum laminate film along with the electrolyte to form a test cell. A 20 μm thick polyethylene was used as the separator, and a 30 μm thick lithium foil was used as the counter electrode. The electrolyte was prepared by dissolving LiPF6 to a concentration of 1 M in a solvent which was a mixture of ethylene carbonate and diethyl carbonate in a 1:1 volume ratio, and then adding 10 wt% fluoroethylene carbonate to this electrolyte.
[0040] [Charge / Discharge Test] A Hokuto Denko SD8 was used as the charge / discharge device. The voltage range was set to 0.005~1.5V, and the current density was set to 0.1C (150mAhg) for the first 1-2 cycles. -1 ) and thereafter 1C (1500Ahg -1 The test was repeated for 200 cycles. The charge / discharge capacity and Coulomb efficiency after 30 and 200 cycles are summarized in Table 1, along with the content of trace elements, SiO, and optional components relative to the SiO particles.
[0041] (Example 2) In Example 1, the negative electrode and charge / discharge test cell were prepared in the same manner as in Example 1, except that the amount of dispersant (CMC) added when preparing the negative electrode coating solution was set to 0 parts by mass (i.e., no dispersant (CMC) was added), and a charge / discharge test was performed. The content of trace elements, SiO, and optional components relative to the SiO particles used, along with the results of the charge / discharge test, are summarized in Table 1.
[0042] (Examples 3-4) Except for changing the content of trace elements, SiO, and optional components as shown in Table 1, the negative electrode and charge / discharge test cell were prepared in the same manner as in Example 1, and charge / discharge tests were performed. The content of trace elements, SiO, and optional components relative to the SiO particles used, along with the results of the charge / discharge tests, are summarized in Table 1. The content of trace elements, SiO, and optional components in the SiO particles was determined using GDMS, where a glow discharge was generated in an argon atmosphere with the sample as the cathode, the sample surface was sputtered in the plasma, and the ionized constituent elements were measured with a mass spectrometer. Specifically, the ionic intensity ratio of the target element including SiO and trace elements was corrected with a relative sensitivity coefficient to obtain semi-quantitative values, which were used as the content of each element.
[0043] [Table 1]
[0044] Further effects and modifications can be readily derived. Therefore, broader aspects of the present invention are not limited to the specific details and representative embodiments expressed and described above. Accordingly, various modifications are possible without departing from the spirit or scope of the overall concept of the invention as defined by the appended claims and their equivalents.
Claims
1. A negative electrode material for lithium-ion batteries, characterized by containing SiO particles that contain one or more trace elements selected from the alkali metal element group consisting of K, Na, and Li, wherein the total content of the said element group is 23 mg / kg or less.
2. The negative electrode material for lithium-ion batteries according to claim 1, characterized in that the SiO particles contain one or more trace elements selected from the group of alkaline earth metal elements consisting of Mg, Ca, Sr, and Ba, and the total content of the group of elements is 3 mg / kg or less.
3. The anode material for lithium-ion batteries according to claim 1, characterized in that the SiO particles contain one or more trace elements selected from Group 4 transition elements consisting of Ti, Zr, and Hf in an amount of 2 mg / kg or less.
4. The negative electrode material for lithium-ion storage batteries according to claim 1, characterized in that the SiO particles contain one or more trace elements selected from Group 6 transition elements consisting of Cr, Mo, and W in an amount of 7 mg / kg or less.
5. The anode material for lithium-ion batteries according to claim 1, characterized in that the SiO particles contain 99.95% by mass or more of SiO.
6. The negative electrode material for lithium-ion storage batteries according to claim 1, characterized in that the SiO particles contain one or more elements selected from the group of other transition elements consisting of Mn, Fe, Co, Ni, Cu, Al, S, and P in an amount of 47 mg / kg or less.
7. The negative electrode material for lithium-ion storage batteries according to claim 1, characterized in that 95 volume percent or more of the SiO particles have a diameter of 0.12 μm or more and 0.90 μm or less.
8. A negative electrode for a lithium-ion battery, comprising a current collector and an active material layer disposed on the current collector, wherein the active material layer includes the negative electrode material for a lithium-ion battery described in any one of claims 1 to 7.
9. The negative electrode for a lithium-ion battery according to claim 8, characterized in that the active material layer comprises one or both of acetylene black and carbon nanotubes.
10. The anode for a lithium-ion battery according to claim 8, characterized in that the active material layer contains at least two of sodium alginate, polyglutamic acid, and polyacrylic acid as binders.
11. The anode for a lithium-ion battery according to claim 8, characterized in that the active material layer contains carboxymethylcellulose as a dispersant.
12. A lithium-ion battery comprising a positive electrode and a negative electrode facing each other with an electrolyte in between, wherein the negative electrode is the negative electrode for a lithium-ion battery described in claim 8.
13. The lithium-ion battery according to claim 12, characterized in that the electrolyte contains lithium ions.
14. The lithium-ion battery according to claim 13, characterized in that the electrolyte includes one of ethylene carbonate and fluoroethylene carbonate.