Preparation method of lithium ion battery negative electrode material with high cycle stability

Abstract

The invention provides a preparation method of a lithium ion battery negative electrode material with high cycle stability, which comprises the following steps: dispersing nanoscale silicon in a solvent, adding artificial graphite, mixing and dispersing uniformly, adding an organic carbon source for compounding, adding a curing agent, mixing and dispersing uniformly, and drying to obtain the lithium ion battery negative electrode material with high cycle stability. And carrying out heat treatment on the dried material in an inert gas atmosphere to obtain a SiG-PF composite material, etching the SiG-PF composite material in a hydrofluoric acid solution, carrying out suction filtration, and drying to obtain the lithium ion battery negative electrode material. By accurately controlling the concentration of hydrofluoric acid, the etching time, the reaction temperature and other parameters, accurate etching of the nano Si particles is achieved, and the particle size of the nano Si particles is effectively reduced.

Description

Technical Field

[0001] The present invention belongs to the field of lithium-ion battery materials, and particularly relates to a preparation method of a negative electrode material for a lithium-ion battery with high cycle stability. Background Art

[0002] Lithium-ion batteries have the advantages of large capacity, large charge and discharge current, long service life, etc., and are widely used in portable devices (such as mobile phones, cameras, laptops), electric and hybrid vehicles, etc., and have great application potential in off-grid power supply systems. With the increasing demand for high-energy-density energy storage devices, traditional lithium-ion battery systems can no longer meet the actual needs, and it is necessary to develop and optimize emerging electrode materials with higher specific capacity.

[0003] Currently, commercially available lithium-ion batteries mainly use graphite materials as negative electrode materials. The reversible specific capacity of carbon materials has reached 360 mAh / g, but its theoretical specific capacity is only 372 mAh / g, indicating that the development of traditional graphite negative electrode materials has approached the limit, but it is still difficult to meet the requirements of future new energy electric vehicles for battery energy density. In order to further improve the energy density of lithium-ion batteries, new high-specific-capacity negative electrode materials have become a research hotspot. Since silicon can form a binary alloy with lithium, and it has the advantages of rich reserves, high theoretical specific capacity, low lithium insertion and extraction potential, and low price, it has become the focus and hotspot of lithium-ion battery research.

[0004] With the deepening of research, we found that although silicon materials have the advantages of high capacity and low lithium deintercalation potential, during the charge and discharge process of silicon-based materials, due to the insertion of lithium ions, they will undergo a huge volume expansion, resulting in the pulverization of the electrode material during the cycle process, and the loss of electrical contact between the active material and the current collector, thus causing rapid capacity decay. Moreover, due to some side reactions occurring during the first charge and discharge, it leads to irreversible loss of active lithium, and its capacity loss is often as high as 40% - 70%, which is closely related to the type, structure, morphology, crystallization state of the material and the components of the electrolyte. The large first irreversible capacity loss consumes a large amount of electrolyte and lithium ions released from the positive electrode material, resulting in a low initial Coulomb efficiency, reducing the energy density and cycle life of the battery. During the industrial development process, the cost of nanosizing silicon is high, and the final particle size of silicon is limited at the nanoscale, and the volume expansion problem of silicon during the charge and discharge process cannot be fundamentally solved. Therefore, the market urgently needs to design new silicon-carbon negative electrode materials for the future development of lithium-ion batteries. Summary of the Invention

[0005] In view of this, the present invention aims to overcome the defects in the prior art and proposes a preparation method of a negative electrode material for a lithium-ion battery with high cycle stability.

[0006] To achieve the above object, the technical solution of the present invention is realized as follows: In a first aspect, the present invention provides a method for preparing a negative electrode material for a lithium-ion battery with high cycle stability, comprising the following steps: Disperse nanoscale silicon in a solvent, then add artificial graphite and mix evenly, then add an organic carbon source for compounding, and then add a curing agent and mix evenly, and then dry. Heat-treat the dried material in an inert gas atmosphere to obtain a SiG@PF composite material. Put the SiG@PF composite material into a hydrofluoric acid solution for etching, then perform suction filtration and drying to obtain the negative electrode material for a lithium-ion battery.

[0007] In some embodiments of the present invention, the concentration of the hydrofluoric acid solution is 1 wt% - 7 wt%.

[0008] In some embodiments of the present invention, the concentration of the hydrofluoric acid solution is 2 wt% - 6 wt%.

[0009] In some embodiments of the present invention, the concentration of the hydrofluoric acid solution is 4 wt%.

[0010] In some embodiments of the present invention, the particle size of the nanoscale silicon is 40 nm - 120 nm.

[0011] In some embodiments of the present invention, the etching temperature is 20 - 50 °C, and the etching time is 10 - 20 min.

[0012] In some embodiments of the present invention, the etching temperature is 25 °C, and the etching time is 15 min.

[0013] In some embodiments of the present invention, the heat treatment temperature is 800 - 900 °C, and the heat preservation time is 1 - 2.5 h.

[0014] In some embodiments of the present invention, the organic carbon source is one or a mixture of two or more of phenolic resin, asphalt, biochar, glucose, and polydopamine.

[0015] In some embodiments of the present invention, the solvent is one or a mixture of two or more of ethanol, tetrahydrofuran, and N-methylpyrrolidone.

[0016] In some embodiments of the present invention, the curing agent is one or a mixture of two or more of hexamethylenetetramine, ethylenediamine, and phthalic anhydride.

[0017] In some embodiments of the present invention, the mass ratio of the organic carbon source, artificial graphite, micron-scale silicon, and curing agent is (1 - 4):(3 - 8):(1 - 4):(0.05 - 0.2).

[0018] In some embodiments of the present invention, the particle size Dv50 of the artificial graphite is 5 - 20 μm.

[0019] In a second aspect, the present invention also provides a negative electrode material for a lithium-ion battery with high cycle stability prepared by the above preparation method.

[0020] In a third aspect, the present invention also provides a lithium-ion battery, wherein the negative electrode material in the lithium-ion battery is the negative electrode material of the present invention described above.

[0021] Compared with the prior art, the present invention has the following advantages: (1) By precisely controlling parameters such as the concentration of hydrofluoric acid, etching time, and reaction temperature, the present invention realizes precise etching of nano-Si particles, effectively reducing the particle size of nano-Si particles. The reduction in the particle size of nano-Si particles alleviates the electrode pulverization phenomenon and effectively extends the service life of the lithium-ion battery. While reducing the particle size of nano-Si particles, their good structural stability is maintained, thereby improving the electrochemical performance of the material and enhancing the cycle stability of the lithium-ion battery.

[0022] (2) The present invention provides a method for suppressing severe electrode pulverization in silicon-based negative electrode materials by reducing the particle size of nano-silicon particles in the silicon-carbon composite material and provides the optimal reaction conditions.

[0023] (3) The operation of the present invention is simple, and the required conditions are easily achieved. A novel coated-structured nano-silicon-carbon negative electrode material with a discharge specific capacity reaching 870 mAh / g and excellent cycle performance can be prepared. Description of the Drawings

[0024] Figure 1 is the thermogravimetric curve of the SiG@PF-4wt% composite material prepared in Example 1 (the thermogravimetric parameters are: the gas atmosphere is air, the heating rate is 5 °C / min, heated to 900 °C, without heat preservation treatment); Figure 2 is the Raman spectrogram of the composite materials prepared in Comparative Example 1 - Comparative Example 2 and Example 1 - Example 3; Figure 3 is the high-magnification transmission electron micrograph of the SiG@PF composite material prepared in Comparative Example 1; Figure 4 is the high-magnification transmission electron micrograph of the SiG@PF-4wt% composite material prepared in Example 1; Figure 5 is the SEM image of the SiG@PF composite material after high-temperature sintering in Example 1; Figure 6 is the SEM image of the SiG@PF-4wt% composite material before cycling in Example 1; Figure 7Cycling performance comparison diagrams of the composite materials prepared in Comparative Examples 1-2 and Examples 1-3; Figure 8 SEM diagram of the SiG@PF composite material prepared in Comparative Example 1 after 100 cycles; Figure 9 SEM diagram of the SiG@PF-4wt% composite material prepared in Example 1 after 100 cycles; Figure 10 Rate performance comparison diagrams of the SiG@PF composite materials prepared in Comparative Examples 1-2 and Examples 1-3 at different current densities; Figure 11 Electrochemical performance diagram of the SiG@P-4wt% composite material prepared in Example 4. Detailed implementation manners

[0025] The embodiments of the present invention will be described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as a limitation to the present invention.

[0026] In this article, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which this application belongs.

[0027] In this article, when a value is described as a range, it should be understood that such disclosure includes the disclosure of all possible sub-ranges within that range, as well as specific numerical values falling within that range, regardless of whether specific numerical values or specific sub-ranges are explicitly indicated.

[0028] In this article, when referring to "multiple", etc., unless otherwise specifically defined, it means greater than 2 or equal to 2 in quantity. For example, "one or more" means one or greater than or equal to two.

[0029] In this article, when referring to "preferred", "more preferred", it is only to describe embodiments or examples with better effects, and it should be understood that it does not constitute a limitation to the protection scope of the present invention.

[0030] In this article, when referring to "further", etc., for descriptive purposes, it represents a difference in content, but should not be construed as a limitation to the protection scope of the present invention.

[0031] In this article, the term "and / or" is a description of the associated relationship of an object, indicating that there can be three relationships. For example, A and / or B means: A or B, or A and B these three relationships.

[0032] In this article, the term "about" means + / - 10% of the specified value, preferably + / - 5%, more preferably + / - 1%.

[0033] As used herein, terms such as "comprising", "including", "having", "containing", etc. are all open-ended terms, meaning including but not limited to.

[0034] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this invention pertains. Although this invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of this invention.

[0035] The present invention will be described in detail below in conjunction with examples.

[0036] Example 1

[0037] Disperse the nano-Si slurry with a Dv50 particle size of 43 nm in an ethanol solution, add artificial graphite with a Dv50 particle size of 8 μm, perform ultrasonic dispersion and magnetic stirring for 30 min each, and then add phenolic resin for compounding. Then perform ultrasonic dispersion for 30 min and add hexamine for magnetic stirring for 8 h (the mass ratio of phenolic resin, artificial graphite, nano-silicon, and hexamine is 2:5:2:0.1); then dry in a blast drying oven at 40 °C, collect the dried material, and obtain the SiG@PF composite material by high-temperature carbonization method in an argon atmosphere in a tube furnace. The heating rate of the tube furnace is 5 °C / min, heat up to 800 °C, and the holding time is 1 h. After taking out the SiG@PF composite material from the tube furnace, grind and sieve it. Take 1 g of the ground SiG@PF composite material and etch it with 4 wt% HF at 25 °C for 15 min to obtain the SiG@PF-4wt% composite material, which is then filtered and dried for use.

[0038] As shown by thermogravimetric analysis, Figure 1 the weight loss rate of the SiG@PF composite material after treatment with 4 wt% HF is 89.6%, and its silicon content is 10.4%.

[0039] The electrochemical performance of the prepared SiG@PF-4wt% composite material is as Figure 7 shown. Compared with the composite material in Comparative Example 1, it has extremely excellent cycle stability performance and rate performance, and after 100 cycles, the capacity has no obvious attenuation.

[0040] Figure 9 is the SEM image of the SiG@PF-4wt% composite material prepared in Example 1 after 100 cycles. Even after 100 cycles of cycling under this condition, the electrode does not show pulverization, and the particle structure remains intact and distinct. This shows that the SiG@PF-4wt% composite material has good structural integrity and can improve the cycle stability of the electrode.

[0041] Example 2

[0042] Disperse the nanoscale Si slurry with a particle size Dv50 of 43 nm in an ethanol solution, add artificial graphite with a particle size Dv50 of 8 μm, ultrasonically disperse and magnetically stir for 30 min each, and then add phenolic resin for compounding. Then ultrasonically disperse for 30 min and add hexamine for magnetic stirring for 8 h (the mass ratio of phenolic resin, artificial graphite, nanoscale silicon, and hexamine is 2:5:2:0.1); then dry in a forced-air drying oven at 40 °C, collect the dried material, and obtain the SiG@PF composite material by high-temperature carbonization in a tubular furnace under an argon atmosphere. The heating rate of the tubular furnace is 5 °C / min, heat up to 800 °C, and the holding time is 1 h. After taking out the SiG@PF composite material from the tubular furnace, grind and sieve it. Take 1 g of the ground SiG@PF composite material and etch it with 2 wt% HF at 25 °C for 15 min to obtain the SiG@PF-2wt% composite material, which is then filtered by suction and dried for use.

[0043] The electrochemical performance of the prepared SiG@PF-2wt% composite material is as Figure 7 and Figure 8 shown. Compared with the composite material in Comparative Example 1, it has extremely excellent cycle stability performance and rate performance, and after 100 cycles, the capacity has no obvious attenuation.

[0044] Example 3

[0045] Disperse the nanoscale Si slurry with a particle size Dv50 of 43 nm in an ethanol solution, add artificial graphite with a particle size Dv50 of 8 μm, ultrasonically disperse and magnetically stir for 30 min each, and then add phenolic resin for compounding. Then ultrasonically disperse for 30 min and add hexamine for magnetic stirring for 8 h (the mass ratio of phenolic resin, artificial graphite, nanoscale silicon, and hexamine is 2:5:2:0.1); then dry in a forced-air drying oven at 40 °C, collect the dried material, and obtain the SiG@PF composite material by high-temperature carbonization in a tubular furnace under an argon atmosphere. The heating rate of the tubular furnace is 5 °C / min, heat up to 800 °C, and the holding time is 1 h. After taking out the SiG@PF composite material from the tubular furnace, grind and sieve it. Take 1 g of the ground SiG@PF composite material and etch it with 6 wt% HF at 25 °C for 15 min to obtain the SiG@PF-6wt% composite material, which is then filtered by suction and dried for use.

[0046] The electrochemical performance of the prepared SiG@PF-6wt% composite material is as Figure 7 shown. Compared with the SiG@PF composite material in Comparative Example 1, it has extremely excellent cycle stability performance and rate performance, and after 100 cycles, the capacity has no obvious attenuation.

[0047] The crystal structures of the composite materials before and after HF modification treatment were studied using Raman spectroscopy. As Figure 2 shown, the peak centered at 510 cm -1 in the SiG@PF composite material without etching treatment corresponds to the Raman phonon vibration of silicon. After HF modification treatment, the silicon peak of the composite material shows a red shift to the left, which is due to the lattice deformation caused by the stress generated in the surrounding Si atomic grid due to the decrease in the particle size of the nano-Si particles by HF etching.

[0048] Example 4

[0049] The nano-Si slurry with a Dv50 particle size of 60 nm was dispersed in a tetrahydrofuran solution, and artificial graphite with a Dv50 particle size of 15 μm was added. After ultrasonic dispersion and magnetic stirring for 30 min each, asphalt was added for compounding. Then ultrasonic dispersion was carried out for another 30 min, and hexamine was added and magnetic stirring was carried out for 8 h (the mass ratio of asphalt, artificial graphite, nano-silicon, and hexamine was 2:5:2:0.1); then it was dried in a blast drying oven at 40 °C, and the dried material was collected and obtained the SiG@P composite material by high-temperature carbonization method in a tubular furnace under an argon atmosphere. The heating rate of the tubular furnace was 5 °C / min, heated to 800 °C, and the holding time was 1 h. After the SiG@P composite material was taken out of the tubular furnace, it was ground and sieved. 1 g of the ground SiG@P composite material was etched with 4 wt% HF at 25 °C for 15 min to obtain the SiG@P-4wt% composite material, which was used after suction filtration and drying.

[0050] The electrochemical performance of the prepared SiG@P-4wt% composite material is as Figure 11 shown. This composite material has extremely excellent electrochemical cycle stability performance, and the capacity does not show obvious attenuation after 100 cycles.

[0051] Example 5

[0052] Disperse the nanoscale Si slurry with a Dv50 particle size of 70 nm in an ethanol solution, add artificial graphite with a particle size of 5 μm, perform ultrasonic dispersion and magnetic stirring for 30 min each, and then add biochar for compounding. Then perform ultrasonic dispersion for 30 min and add ethylenediamine for magnetic stirring for 8 h (the mass ratio of biochar, artificial graphite, nanoscale silicon, and ethylenediamine is 1:8:1:0.2); then dry in a blast drying oven at 40 °C, collect the dried material, and use high-temperature carbonization in a tubular furnace under an argon atmosphere to obtain the SiG@PF composite material. The heating rate of the tubular furnace is 5 °C / min, heat up to 900 °C, and the holding time is 1.5 h. After taking out the SiG@PF composite material from the tubular furnace, grind and sieve it. Take 1 g of the ground SiG@PF composite material, etch it with 1 wt% HF at 20 °C for 20 min to obtain the SiG@PF-1wt% composite material, and use it after filtration and drying.

[0053] Example 6

[0054] Disperse the nanoscale Si slurry with a Dv50 particle size of 120 nm in an ethanol solution, add artificial graphite with a particle size of 20 μm, perform ultrasonic dispersion and magnetic stirring for 30 min each, and then add polydopamine for compounding. Then perform ultrasonic dispersion for 30 min and add phthalic anhydride for magnetic stirring for 8 h (the mass ratio of polydopamine, artificial graphite, nanoscale silicon, and phthalic anhydride is 4:3:4:0.05); then dry in a blast drying oven at 40 °C, collect the dried material, and use high-temperature carbonization in a tubular furnace under an argon atmosphere to obtain the SiG@PF composite material. The heating rate of the tubular furnace is 5 °C / min, heat up to 800 °C, and the holding time is 2.5 h. After taking out the SiG@PF composite material from the tubular furnace, grind and sieve it. Take 1 g of the ground SiG@PF composite material, etch it with 7 wt% HF at 50 °C for 10 min to obtain the SiG@PF-7wt% composite material, and use it after filtration and drying.

[0055] Comparative Example 1 Disperse the nanoscale Si slurry with a Dv50 particle size of 43 nm in an ethanol solution, add artificial graphite with a particle size of 8 μm, perform ultrasonic dispersion and magnetic stirring for 30 min each, and then add phenolic resin for compounding. Then perform ultrasonic dispersion for 30 min and add hexamethylenetetramine for magnetic stirring for 8 h (the mass ratio of phenolic resin, artificial graphite, nanoscale silicon, and hexamethylenetetramine is 2:5:2:0.1); then dry in a blast drying oven at 40 °C, collect the dried material, and use high-temperature carbonization in a tubular furnace under an argon atmosphere to obtain the SiG@PF composite material. The heating rate of the tubular furnace is 5 °C / min, heat up to 800 °C, and the holding time is 1 h. Take out the SiG@PF composite material from the tubular furnace, and use it after grinding and sieving.

[0056] The electrochemical performance of the prepared SiG@PF composite material is as Figure 7 shown. It can be seen that after 20 cycles, there is a trend of significant capacity decay, and the capacity retention rate after 100 cycles is only 57.6%, and it has poor rate performance. Figure 8 Figure 6 is the SEM image of the SiG@PF composite material prepared in Comparative Example 1 after 100 cycles. The silicon nanoparticles of the SiG@PF composite material fail to maintain a complete structure, and there is a phenomenon of particle fragmentation. The contact of the fragmented particles with each other will have an adverse effect on the cycling stability.

[0057] Comparative Example 2 Disperse the nanoscale Si slurry with a Dv50 particle size of 43 nm in an ethanol solution, add artificial graphite with a particle size of 8 μm, perform ultrasonic dispersion and magnetic stirring for 30 min each, and then add phenolic resin for compounding. Then perform ultrasonic dispersion for 30 min and add hexamethylenetetramine for magnetic stirring for 8 h (the mass ratio of phenolic resin, artificial graphite, nanoscale silicon, and hexamethylenetetramine is 2:5:2:0.1); then dry in a forced-air drying oven at 40 °C, collect the dried material, and obtain the SiG@PF composite material by high-temperature carbonization method in a tubular furnace under an argon atmosphere. The heating rate of the tubular furnace is 5 °C / min, heat up to 800 °C, and the holding time is 1 h. After taking out the SiG@PF composite material from the tubular furnace, grind and sieve it. Take 1 g of the ground SiG@PF composite material and etch it with 8 wt% HF at 25 °C for 15 min to obtain the SiG@PF-8wt% composite material, which is used after filtration and drying.

[0058] The electrochemical performance of the prepared SiG@PF-8wt% composite material is as Figure 7 shown. It can be seen that after 20 cycles, there is a trend of significant capacity decay, and the capacity retention rate after 100 cycles is only 42.8%, and it has poor rate performance.

[0059] Figure 3 and Figure 4 Figures 7 and 8 are the high-magnification transmission electron microscope images of the SiG@PF prepared in Comparative Example 1 and the SiG@PF-4wt% composite material prepared in Example 1, respectively. It can also be seen that the particle size of the Si particles decreases after HF etching.

[0060] Figure 5 Figure 9 is the SEM image of the SiG@PF composite material after high-temperature sintering in Comparative Example 1. The mixing of nano-silicon particles and graphite is relatively uneven and the arrangement of graphite layers is chaotic. A large number of silicon particles can be clearly observed adhering to the surface of flaky graphite, which will affect the conductivity of the composite material. Figure 6Figure (a) shows the SEM image of the SiG@PF-4wt% composite before cycling. After HF etching treatment, the silicon particles on the surface of flaky graphite decrease, and the nanosilicon particles and graphite layers are well mixed. This structure can greatly enhance the conductivity of the composite material and thus improve its electrochemical performance.

[0061] Figure 10 Figure (b) shows the rate performance comparison of the SiG@PF composites prepared in Comparative Example 1 - Comparative Example 2 and Example 1 - Example 3 at different current densities. It can be seen that the SiG@PF-4wt% composite has the best rate performance. Even at a rate of 1 C, it still has a reversible specific capacity of 539.7 mA·h·g -1 . In contrast, the capacity of the SiG@PF composite rapidly decays to 200 mA·h·g at a rate of 1 C -1 , showing extremely poor rate performance.

[0062] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A preparation method of a negative electrode material for a lithium-ion battery with high cycle stability, characterized in that: It includes the following steps: Disperse nanoscale silicon in a solvent, then add artificial graphite and mix evenly. After that, add an organic carbon source for compounding, and then add a curing agent and mix evenly, followed by drying. Heat-treat the dried material in an inert gas atmosphere to obtain the SiG@PF composite material. Etch the SiG@PF composite material in a hydrofluoric acid solution, then perform suction filtration and drying to obtain the anode material for a lithium-ion battery.

2. The preparation method of the anode material for a lithium-ion battery with high cycle stability according to claim 1, characterized in that: The concentration of the hydrofluoric acid solution is 1 wt% - 7 wt%.

3. The preparation method of the anode material for a lithium-ion battery with high cycle stability according to claim 1, characterized in that: The particle size of the nanoscale silicon is 40 nm - 120 nm.

4. The preparation method of the anode material for a lithium-ion battery with high cycle stability according to claim 1, characterized in that: The temperature of the etching is 20 - 50 °C, and the etching time is 10 - 20 min.

5. The preparation method of the anode material for a lithium-ion battery with high cycle stability according to claim 1, characterized in that: The temperature of the heat treatment is 800 - 900 °C, and the holding time is 1 - 2.5 h.

6. The preparation method of the anode material for a lithium-ion battery with high cycle stability according to claim 1, characterized in that: The organic carbon source is one or a mixture of two or more of phenolic resin, pitch, biochar, glucose, and polydopamine; and / or The curing agent is one or a mixture of two or more of hexamethylenetetramine, ethylenediamine, and phthalic anhydride; and / or The solvent is one or a mixture of two or more of ethanol, tetrahydrofuran, and N-methylpyrrolidone.

7. The preparation method of the anode material for a lithium-ion battery with high cycle stability according to claim 1, characterized in that: The mass ratio of the organic carbon source, artificial graphite, nanoscale silicon, and curing agent is (1 - 4):(3 - 8):(1 - 4):(0.05 - 0.2).

8. The preparation method of the anode material for a lithium-ion battery with high cycle stability according to claim 1, characterized in that: The particle size Dv50 of the artificial graphite is 5 - 20 μm.

9. An anode material for a lithium-ion battery with high cycle stability prepared by the preparation method according to any one of claims 1 - 8.

10. A lithium-ion battery, wherein the anode material in the lithium-ion battery is the anode material for a lithium-ion battery with high cycle stability according to claim 8.

Images