Composite negative electrode material, preparation method thereof and battery

Abstract

The invention relates to a composite negative electrode material, a preparation method thereof and a battery, and belongs to the technical field of battery materials, the composite negative electrode material comprises a modified silicon oxide, a carbon material layer and a zirconium-containing coating layer from inside to outside; the modified silicon oxide is a metal element doped and modified silicon oxide; the metal elements comprise magnesium and aluminum; the mass of the carbon material layer accounts for 60-72% of the mass of the composite negative electrode material; the zirconium-containing coating layer is phosphate of nano amorphous zirconium; and the molar ratio of the zirconium element in the zirconium-containing coating layer to the silicon element in the modified silicon oxide is (0.01-0.1): 1. The composite negative electrode material provided by the invention is stable in structure, small in volume expansion, low in resistivity, high in conductivity and good in cycling stability, and a battery (such as a liquid battery, a solid battery and a semi-solid battery) containing the composite negative electrode material has relatively high first charge-discharge performance, relatively long cycle life and relatively low volume expansion rate.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and in particular to a composite negative electrode material, its preparation method, and a battery thereof. Background Technology

[0002] With societal development, higher demands are being placed on the energy density and cycle life of lithium-ion batteries. The existing graphite anode has a theoretical specific capacity of only 372 mAh / g, which is insufficient to meet future energy density requirements. Silicon-based anodes, due to their high theoretical specific capacity, abundant content, and suitable lithium intercalation potential, are gradually becoming the next-generation lithium-ion battery anode material that can replace graphite. However, silicon-based anode materials still face some pressing problems that need to be solved.

[0003] (1) When silicon-based anode materials undergo an irreversible reaction during the first lithium insertion, the generated byproduct Li2O does not participate in the subsequent delithiation process, resulting in the permanent loss of active lithium, which in turn leads to a decrease in the first charge and discharge performance of the battery prepared from it. (2) The lithium storage mechanism of silicon-based anode materials is alloying lithium storage. During the alloying / dealloying process (cycle charging and discharging), silicon particles will cause huge volume expansion and contraction. When silicon and lithium form Li 15 When the Si4 phase is in place, the maximum volume expansion can reach 300%. This extreme volume expansion not only causes the silicon material to pulverize, resulting in poor electrical contact between the silicon particles and the conductive agent, leading to poor conductivity, but also prevents electrons from being effectively transported in the electrodes. This results in excessive polarization, high resistivity, low conductivity, poor cycle stability, and low capacity retention, especially with severe capacity decay under fast charge cycle conditions. Batteries made from this material exhibit decreased initial charge-discharge performance, high volume expansion rate, poor cycle stability, and severe battery aging.

[0004] (3) The silicon-based anode material and the lithium and electrolyte components in the cathode material will undergo side reactions. The presence of side reactions will prevent the silicon-based anode material from fully utilizing its capacity during the first discharge, resulting in poor first charge and discharge performance. Furthermore, side reactions will continue to occur during the charge and discharge process, and the volume expansion will also cause the SEI film to continuously rupture and regenerate. All of these processes will consume a large amount of active lithium or electrolyte in the cathode material, accelerating the capacity decay and aging of the battery (especially under fast charge cycle conditions).

[0005] Therefore, developing a silicon-based anode material that can effectively suppress irreversible reactions during the first lithium insertion of silicon-based anode materials and volume expansion during charging and discharging, and can isolate silicon-based materials from contact and reaction with cathode materials or electrolytes, has important research significance and application value. Summary of the Invention

[0006] To address one or more technical problems existing in the prior art, the present invention provides a composite anode material, its preparation method, and a battery. The composite anode material has a stable structure, small volume expansion, good conductivity, low resistivity, high electrical conductivity, and good cycle stability. The battery containing the composite anode material has high initial charge-discharge performance, better cycle life under fast charging cycle, and low volume expansion rate.

[0007] The present invention provides a composite anode material in a first aspect, the composite anode material comprising, from the inside out, a modified silicon oxide, a carbon material layer, and a zirconium-containing coating layer; the modified silicon oxide is a silicon oxide modified by metal element doping; the metal element includes magnesium and aluminum; the mass of the carbon material layer accounts for 60-72% of the mass of the composite anode material; the zirconium-containing coating layer is a phosphate of nano-amorphous zirconium; the molar ratio of zirconium element in the zirconium-containing coating layer to silicon element in the modified silicon oxide is 0.01-0.1:1.

[0008] Preferably, in the modified silicon oxide, the molar ratio of the metal element to the silicon element is 0.1 to 1:1; and / or The molar ratio of magnesium to aluminum in the metal elements is 0.5 to 2:1.

[0009] Preferably, the carbon material is at least one of carbon nanotubes and graphene; and / or The zirconium phosphate is at least one of Zr(HPO4)2 and Zr(H2PO4)4, preferably Zr(HPO4)2.

[0010] In a second aspect, the present invention provides a method for preparing the composite negative electrode material described in the first aspect, the method comprising: S1. A dispersion containing the modified silicon oxide, carbon source and reducing agent is subjected to a hydrothermal reaction to form a carbon material layer on the surface of the modified silicon oxide, thereby obtaining the modified material; S2. The dispersion containing the modified material, zirconium source, and phosphate source is subjected to a solvothermal reaction to form a zirconium-containing coating layer, thereby obtaining a composite anode material.

[0011] Preferably, in step S1, the mass ratio of the modified silicon oxide, carbon source, and reducing agent is 28~37:60~70:2~3; The carbon source is at least one of graphene oxide and carbon nanotubes; and / or The hydrothermal reaction is carried out at a temperature of 160-180℃ for 2-4 days.

[0012] Preferably, the reducing agent is hydrazine hydrate.

[0013] Preferably, in step S2, the molar ratio of silicon in the modified material to zirconium in the zirconium source is 1:0.01~0.1; and / or The solvothermal reaction is carried out at a temperature of 170-200℃ for 2-4 days.

[0014] Preferably, the zirconium source is ZrO powder; the phosphate source is at least one of (NH4)2HPO4 and NH4H2PO4; and / or The solvent in the dispersion includes water and alcohol.

[0015] In a third aspect, the present invention provides a battery comprising the composite negative electrode material described in the first aspect.

[0016] Preferably, the battery is a liquid battery, a semi-solid battery, or a solid battery.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: This invention uses magnesium and aluminum co-doped modified silicon oxide as the core, and sequentially coats it with a carbon material layer and a zirconium-containing coating layer. This effectively suppresses irreversible side reactions during the first lithium insertion of silicon-based anode materials and the volume expansion of silicon oxide during charge-discharge cycles. It also effectively avoids contact and reaction between silicon oxide and cathode materials, electrolytes, etc., thereby effectively improving the structural stability, conductivity, and cycle stability of the composite anode material, reducing resistivity, and improving the first charge-discharge performance and cycle life of batteries when applied to batteries, while reducing the volume expansion rate. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] The present invention provides a composite anode material in a first aspect, the composite anode material comprising, from the inside out, a modified silicon oxide, a carbon material layer, and a zirconium-containing coating layer; the modified silicon oxide is a silicon oxide modified by metal element doping; the metal element includes magnesium and aluminum; the mass of the carbon material layer accounts for 60-72% of the mass of the composite anode material; the zirconium-containing coating layer is a phosphate of nano-amorphous zirconium; the molar ratio of zirconium element in the zirconium-containing coating layer to silicon element in the modified silicon oxide is 0.01-0.1:1.

[0020] This invention uses magnesium and aluminum co-doped modified silicon oxide as the core, and sequentially coats it with a carbon material layer and a zirconium-containing coating layer. This effectively suppresses the irreversible reaction of silicon-based anode materials during the first lithium insertion and the volume expansion of silicon oxide during charge-discharge cycles. It also effectively avoids contact and reaction between silicon oxide and cathode materials, electrolytes, etc., thereby effectively improving the structural stability, conductivity, and cycle stability of the composite anode material, reducing resistivity, and improving the first charge-discharge performance and cycle life of the battery when applied to batteries, while reducing the volume expansion rate.

[0021] In silicon-based anode materials, coating silicon-based materials with carbon materials can, to some extent, suppress the volume expansion of silicon-based anode materials, isolate the silicon-based anode materials from contact and reaction with cathode materials and electrolytes, improve the conductivity and cycle performance of anode materials, and improve the first charge-discharge performance and cycle life of batteries when applied to batteries, while reducing the volume expansion rate. However, the carbon material coating layer has limited effect on suppressing irreversible side reactions during the first lithium insertion of silicon-based materials and the volume expansion during charge and discharge processes, and cannot effectively prevent contact and reaction between silicon-based materials and cathode materials and electrolytes during long-term charge and discharge processes, so the performance improvement is limited.

[0022] The inventors of this invention also attempted to use zirconium phosphate as a zirconium-containing coating layer to directly coat silicon oxide as a negative electrode material. By forming covalent bonds between silicon oxide and zirconium phosphate, the stability of the composite negative electrode material can be improved, and the reaction between silicon oxide and positive electrode material, electrolyte, etc. can be reduced. However, the zirconium-containing coating layer also cannot effectively suppress the irreversible reaction during the first lithium insertion of the negative electrode material and the volume expansion during the charge and discharge process. Moreover, the uniformity of the zirconium-containing coating layer formed by directly coating zirconium phosphate on silicon oxide is poor, the utilization rate of zirconium element is low, the improvement of electronic conductivity is limited, and the problem of limited lithium-ion transport cannot be solved.

[0023] The inventors of this invention discovered through research that using magnesium and aluminum co-doped modified silicon oxide as a core, and sequentially coating it with a carbon material layer and a zirconium-containing coating layer, can effectively suppress irreversible side reactions during the initial lithium insertion of silicon oxide and volume expansion during charge and discharge. This also effectively avoids contact and reaction between silicon oxide and the cathode material, electrolyte, etc., thereby effectively improving the structural stability, conductivity, and cycle performance of the composite anode material, reducing resistivity, and improving the initial charge and discharge performance and cycle life of the battery when applied to batteries, while reducing the volume expansion rate. Specifically: First, magnesium and aluminum, as metallic elements, have high electrical conductivity, and their doping can improve the conductivity of the modified silicon oxide core to a certain extent. Through Mg / Al co-doping, the electronic structure can be tuned to improve conductivity (mechanism: increased carrier concentration: Mg...). 2+ →Si 4+ +2e -Al 3+ →Si 4+ +e - This improves electronic conductivity; furthermore, co-doping with aluminum and magnesium allows them to form strong functional groups with oxygen (and Si) in silicon oxide (SiOx). , Mg-O and Al-O bonds are more stable than Si-O bonds, which can anchor the SiOx framework, suppress structural collapse during lithium intercalation, and effectively stabilize the silicon-oxygen chain structure. On the one hand, this can prevent irreversible reactions of silicon oxide during the first lithium intercalation to generate the byproduct Li2O, thus avoiding a decrease in performance during the first charge-discharge cycle. On the other hand, it can increase the average chain length and even cause slight polymerization between silicon-oxygen chains (the inventors found that silicon-oxygen chains without Mg / Al co-doping will break, generating more defect vacancies, leading to structural collapse and microcrack formation). This slows down the structural collapse of the electrode material during charge-discharge processes, especially during fast-charge cycles. In other words, through magnesium-aluminum co-doping, the volume expansion of modified silicon oxide can be effectively avoided, and good electrical contact between silicon oxide and carbon material layer can be achieved. Combined with the coating of highly conductive carbon material layer, it can effectively suppress the irreversible reaction of the negative electrode material during the first lithium intercalation and the volume expansion during charge-discharge processes, and significantly reduce resistivity, improve conductivity and cycle stability.

[0024] Secondly, coating modified silicon oxide with carbon material can further effectively suppress the volume expansion of silicon-based anode materials, isolate silicon-based anode materials from contact and reaction with cathode materials and electrolytes, improve the conductivity and cycle performance of anode materials, and improve the first charge-discharge performance and cycle life of batteries when applied to batteries, while reducing the volume expansion rate.

[0025] Furthermore, after coating the modified silicon oxide with carbon material, it is then coated with zirconium-containing phosphate. On the one hand, the functional groups in the modified silicon oxide... This method can increase the oxygen active sites in modified silicon oxides. These active sites can form CO bonds with C elements in carbon materials and Zr-O bonds with zirconium elements in zirconium-containing phosphates, thereby improving the stability of composite anode materials, reducing side reactions between silicon oxides and cathode materials, electrolytes, etc., and the utilization rate of zirconium elements is relatively high. Zirconium elements can serve as central active sites, which can not only improve the weakness of silicon oxides in lithiation / delithiation reactions, but also adsorb solvated lithium ions, improve the lithium ion insertion efficiency in silicon oxides, and further enhance conductivity and cycle stability. The initial charge-discharge performance of the prepared battery is also significantly improved, and the cycle stability is excellent.

[0026] In addition, the magnesium and aluminum doping in the modified silicon oxide can form chemical bonds such as Al-O-Li and Mg-O-Li when Li is inserted into the negative electrode, promoting the regular arrangement of lithium and ensuring the charging capacity. When Li is extracted from the negative electrode, magnesium or aluminum ions can replace the Li position, thereby maintaining the interlayer distance of the negative electrode material, which is beneficial to the discharge capacity and can effectively suppress irreversible lithium ion loss in the first cycle of the battery. Furthermore, the zirconium element in the zirconium-containing coating layer can serve as a central active site, which can not only improve the weak activity of silicon oxide in the lithiation / delithiation reaction, but also adsorb solvated lithium ions, improve the lithium ion insertion efficiency in silicon oxide, and further improve the cycle life of the composite negative electrode material, as well as the first charge-discharge performance and cycle life of the battery made from it.

[0027] The composite anode material provided by this invention achieves a stable structure, small volume expansion, low resistivity, high conductivity, and good cycle stability through the synergistic enhancement effect of metal doping, carbon material layer, and zirconium-containing coating layer. Batteries containing this composite anode material (e.g., liquid batteries, solid-state batteries, and semi-solid batteries) have higher initial charge-discharge performance, better cycle life, and lower volume expansion rate.

[0028] According to some preferred embodiments, in the modified silicon oxide, the molar ratio of the metal element to the silicon element is 0.1 to 1:1.

[0029] First, by adjusting the molar ratio of metal elements to silicon elements, the functional groups can be better controlled. , The formation of LiOx bonds, utilizing the superior stability of Mg-O and Al-O bonds compared to Si-O bonds, can anchor the SiOx framework, suppress structural collapse during lithium intercalation, and further stabilize the silicon-oxygen chain structure, preventing irreversible reactions during the initial lithium intercalation and controlling the average chain length to avoid volume expansion of silicon oxides. Secondly, controlling the molar ratio of metal elements to silicon elements within the aforementioned range can improve the formation of LiOx. x SiO y The formation energy barrier of intermediate phases such as Li₄SiO₄ is lowered, thereby promoting the forward direction of the reversible lithium intercalation reaction; in addition, the electronic structure can be tuned through Mg / Al doping, further improving the conductivity (mechanism: increased carrier concentration: Mg). 2+ →Si 4+ +2e - Al 3+ →Si 4+ +e - (This improves electronic conductivity); furthermore, by controlling the molar ratio of metal elements to silicon elements within the aforementioned range, the synergistic effect of Mg-Al co-doping can be achieved (compared to traditional single-magnesium-doped silicon-oxygen materials, Al...).3+ The incorporation of [a substance] can balance Mg. 2+ The introduced excess positive charge reduces lattice distortion, and , Clusters can enhance the rigidity of the local structure and maintain high ionic conductivity.

[0030] The inventors discovered that if the doping amount of the metal element is too low, the effect on suppressing the irreversible reaction during the initial lithium intercalation of silicon oxide and the volume expansion during charge and discharge is weakened, leading to decreased electronic conductivity (low current concentration, high resistance), poor volume expansion suppression (discontinuous mechanical support network), and poor interface stability (increased organic content in the negative electrode SEI film, resulting in low initial efficiency). If the doping amount of the metal element is too high, the structural stability of silicon oxide is damaged, and lattice distortion is aggravated: due to Mg... 2+ (0.72Å) and Al 3+ The ionic radius of (0.54 Å) is similar to that of Si. 4+ The difference (0.40 Å) is significant. Excessive doping can introduce severe lattice stress, leading to local structural disorder. Since the amorphous / crystalline mixed structure of silicon-oxygen itself is sensitive to doping, excessive doping may induce phase separation, forming electrochemically inert regions, thereby reducing electronic / ionic conductivity. Secondly, doped ions occupy lithium diffusion channels (such as interstitial sites), especially with high concentrations of doping, which can block lithium-ion transport paths and increase polarization. Furthermore, highly doped silicon-oxygen materials are prone to microcracks, leading to local stress concentration in silicon-oxygen. During charging and discharging, lithium insertion / extraction will further amplify the stress, resulting in electrode pulverization. In addition, excessive Mg / Al doping may expose highly active surfaces (unreacted metal clusters), catalyzing electrolyte decomposition (such as generating more LiF, ROCO2Li), consuming active lithium interfaces, and exacerbating side reactions, resulting in a decrease in first-cycle coulombic efficiency (first-cycle efficiency).

[0031] According to some preferred embodiments, the molar ratio of magnesium to aluminum in the metallic elements is 0.5 to 2:1.

[0032] This invention can also control the functional groups by adjusting the molar ratio of magnesium and aluminum. , The formation of the number of ions is crucial to better avoid irreversible reactions during the first lithium insertion of silicon oxide and volume expansion during charging and discharging. If one of them is too much and the other is too little, it may reduce the number of related chemical bonds (Mg-O bonds and Al-O bonds), thereby weakening the anchoring effect on the SiOx framework, reducing the stability of the silicon oxide chain structure, and reducing the inhibitory effect on the volume expansion of silicon oxide.

[0033] According to some preferred embodiments, the carbon material is at least one of carbon nanotubes and graphene.

[0034] Conventional carbon materials in this field can be used in the composite anode material of this invention to improve the electronic conductivity of the composite anode material. Additionally, they can suppress volume expansion of the composite anode material to a certain extent and avoid the recurrence of silicon oxide side reactions, thereby increasing the specific capacity of the composite anode material. When used in batteries, they improve the initial charge-discharge efficiency, cycle life, and capacity retention, while reducing the volume expansion rate. During their research, the inventors discovered that using carbon nanotubes (CNTs) as the carbon material, leveraging their large aspect ratio, specific surface area, and numerous active sites, not only provides longer electron transport pathways but also provides more active sites for lithium-ion insertion / extraction, thus improving the material's ability to conduct current and transfer energy, meeting the needs of fast charge and discharge applications. Furthermore, using carbon nanotubes as the carbon material effectively solves the problem that existing conductive carbon mainly relies on point contacts between particles, resulting in a zero-dimensional conductive network that requires a large amount to achieve optimal conductivity. Using graphene as the carbon material can effectively improve the electron transport rate of the composite material in the electrode, reduce battery internal resistance, and thus improve charge-discharge performance, significantly increasing the battery's charge-discharge efficiency.

[0035] According to some preferred embodiments, the zirconium phosphate is at least one of Zr(HPO4)2 and Zr(H2PO4)4, preferably Zr(HPO4)2.

[0036] The zirconium-containing coating of the present invention is a nano-amorphous zirconium phosphate (nano-amorphous Zr(HPO4)2 or nano-amorphous Zr(H2PO4)4), which has excellent lithium-ion adsorption performance, can provide a fast conduction interface for lithium ions, promote electron transport on the material surface, improve the stability of the material's structure and physicochemical properties, alleviate the volume expansion of the material, reduce the occurrence of surface side reactions, and thus improve the cycle life of lithium-ion batteries.

[0037] During their research, the inventors discovered that selecting nano-amorphous Zr(HPO4)2 as a zirconium-containing coating layer not only facilitates lithium-ion conduction and improves the material's conductivity, but also maintains the stability of the electrode material structure during repeated charge-discharge cycles, reducing electrode material degradation and extending battery life.

[0038] In a second aspect, the present invention provides a method for preparing the composite negative electrode material described in the first aspect, the method comprising: S1. A dispersion containing the modified silicon oxide, carbon source and reducing agent is subjected to a hydrothermal reaction to form a carbon material layer on the surface of the modified silicon oxide, thereby obtaining the modified material; S2. The dispersion containing the modified material, zirconium source, and phosphate source is subjected to a solvothermal reaction to form a zirconium-containing coating layer, thereby obtaining a composite anode material.

[0039] This invention first forms a uniformly distributed carbon material layer on the surface of modified silicon oxide (Mg / Al-SiOx) using a hydrothermal method, and then forms a zirconium-containing coating layer (phosphate of nano-amorphous zirconium) on the material surface using a solvothermal method, thus obtaining a composite anode material. Due to the chemical bonds in the modified silicon oxide... This method can increase the oxygen active sites in modified silicon oxides. These active sites can form CO bonds with C elements in carbon materials or Zr-O bonds with zirconium elements in zirconium-containing phosphates, thereby forming a uniform carbon material layer and a zirconium-containing coating layer. The composite anode material prepared by this method has a stable structure, small volume expansion, low resistivity, high conductivity, and good cycle stability. Batteries containing this composite anode material (e.g., liquid batteries, solid-state batteries, semi-solid batteries) have high initial charge-discharge performance, better cycle life, and lower volume expansion rate.

[0040] This invention does not impose specific limitations on the process parameters for preparing modified silicon oxides. The parameters can be selected by referring to the existing preparation processes for metal-doped modified silicon oxides, as long as the modified silicon oxides that meet the requirements can be obtained.

[0041] The present invention also provides a more suitable preparation process for modified silicon oxide to better obtain modified silicon oxide. The preparation method includes: mixing silicon, silicon oxide, magnesium-containing materials and aluminum-containing materials, and then subjecting them to a thermal reduction disproportionation reaction to obtain modified silicon oxide.

[0042] According to some preferred embodiments, the magnesium-containing material includes at least one of magnesium and magnesium salts.

[0043] According to some preferred embodiments, the aluminum-containing material includes at least one of aluminum and aluminum salts.

[0044] According to some preferred embodiments, the vacuum degree of the thermal reduction disproportionation reaction is 30~100Pa, the reaction temperature is 1000~1200℃, and the reaction time is 48~96h.

[0045] According to some preferred embodiments, the molar ratio of magnesium in magnesium-containing materials to aluminum in aluminum-containing materials is 0.5~2:1.

[0046] This invention uses the above-mentioned low-temperature vacuum thermal reduction disproportionation reaction to prepare magnesium and aluminum doped modified silicon oxides, which not only reduces the energy consumption of the reaction and ensures the mildness and uniformity of the reaction, but also obtains structurally complete modified silicon oxide particles with uniform pore distribution and significantly refined grains, thereby greatly reducing the volume change during the cycling process.

[0047] According to some preferred embodiments, in step S1, the mass ratio of the modified silicon oxide, carbon source and reducing agent is 28~37:60~70:2~3.

[0048] The inventors discovered that controlling the amount of the three components within this range can reasonably regulate the thickness and coating uniformity of the carbon material layer, thereby better improving the performance of the composite anode material.

[0049] According to some preferred embodiments, in step S1, the carbon source is at least one of graphene oxide and carbon nanotubes.

[0050] When the carbon source is graphene oxide, the reducing agent is used to reduce the graphene oxide to graphene, thus achieving the coating of graphene on the surface of modified silicon oxide. When the carbon source is carbon nanotubes, the reducing agent is used to reduce the oxygen-containing groups on the surface of carbon nanotubes to avoid the oxygen-containing groups affecting the performance of carbon nanotubes, specifically manifested as decreased conductivity, poor dispersibility, reduced chemical stability, weakened mechanical properties, limited adsorption activity, and poor interfacial compatibility.

[0051] According to some preferred embodiments, in step S1, the temperature of the hydrothermal reaction is 160~180℃ and the time is 2~4 days.

[0052] According to some preferred embodiments, the reducing agent is hydrazine hydrate. This invention does not specifically limit the type of reducing agent, as long as it meets the reduction requirements. In some preferred embodiments, this invention preferably uses hydrazine hydrate, which has mild reaction conditions and is environmentally friendly, as the reducing agent.

[0053] According to some preferred embodiments, in step S2, the molar ratio of silicon in the modified material to zirconium in the zirconium source is 1:0.01~0.1. This invention does not specifically limit the amount of zirconium in the zirconium source to phosphorus in the phosphate source, as long as it satisfies the requirement for forming a zirconium-containing coating layer. To better form the zirconium-containing coating layer, this invention preferably uses the above-mentioned range for the molar ratio of silicon in the modified material to zirconium in the zirconium source.

[0054] According to some preferred embodiments, the temperature of the solvothermal reaction is 170~200°C and the time is 2~4 days.

[0055] According to some preferred embodiments, the zirconium source is ZrO powder; the phosphate source is at least one of (NH4)2HPO4 and NH4H2PO4. Preferably, ZrO powder is used as the zirconium source, and (NH4)2HPO4 or NH4H2PO4 is used as the phosphate source, to avoid the introduction of impurity elements affecting the performance of the negative electrode material.

[0056] According to some preferred embodiments, the solvent in the dispersion includes water and alcohol. This invention does not specifically limit the solvent of the dispersion, as long as it allows for uniform mixing of the components. During the research process, this invention discovered that when the solvent includes water and alcohol, it is beneficial for dispersing the modified material, zirconium source, and phosphate source to obtain a uniform dispersion.

[0057] In a third aspect, the present invention provides a battery comprising the composite negative electrode material described in the first aspect.

[0058] According to some preferred embodiments, the battery is a liquid battery, a semi-solid battery, or a solid battery.

[0059] To more clearly illustrate the technical solution and advantages of the present invention, the present invention will be further described below with reference to embodiments. The present invention does not specifically limit the source of the reagents used in the embodiments and comparative examples; they can be directly purchased or synthesized in-house.

[0060] Example 1 A composite anode material comprises, from the inside out, a modified silicon oxide, a carbon material layer, and a zirconium-containing coating layer; the modified silicon oxide is a magnesium-aluminum co-doped modified silicon oxide; in the modified silicon oxide, the ratio of the total molar number of magnesium and aluminum elements to the molar number of silicon elements is 0.5:1; the molar ratio of magnesium to aluminum elements is 1:1; the carbon material layer (graphene) accounts for approximately 70.7 wt% of the composite anode material; the molar ratio of zirconium elements in the zirconium-containing coating layer (Zr(HPO4)2 layer) to silicon elements in the modified silicon oxide is 0.02:1; The preparation method of this composite anode material includes: S1. Carbon coating layer: Modified silicon oxide (Mg / Al-SiO2) x The modified silicon oxide, carbon material, and hydrazine hydrate solution were mixed, with a mass ratio of 28:70:2. The mixture was ultrasonically stirred and then transferred to a reactor for hydrothermal reaction (180℃ for 2 days). After cooling to room temperature, filtration, and washing, a graphene-coated composite material (Mg / Al-SiO₂) was obtained. X@Gr materials). The method for preparing modified silicon oxide includes: mixing silicon (average particle size approximately 100 nm), silicon dioxide (average particle size approximately 10 μm), aluminum-containing materials (containing aluminum and aluminum chloride in a molar ratio of 1:1), and magnesium-containing materials (containing magnesium and magnesium chloride in a molar ratio of 1:1), pressing them into spheres, and then feeding them into a vacuum furnace. The temperature inside the vacuum furnace is heated to 1200℃, and the vacuum degree inside the vacuum furnace is controlled at 100 Pa. A thermal reduction disproportionation reaction is carried out for 2 days to obtain modified silicon oxide (Mg / Al-SiOx material); wherein the molar ratio of magnesium in silicon, silicon dioxide, and magnesium-containing materials to aluminum in aluminum-containing materials is 1:1:0.5:0.5.

[0061] S2. Zirconium-containing coating: Mg / Al-SiO X @Gr material (molecular weight approximately 639.52 g / mol, weight 639.52 g), a suspension of ZrO powder dispersed in water, and a (NH4)2HPO4 solution (a mixed solvent of water, isopropanol, and ethylene glycol) were mixed and ultrasonically stirred. The homogenized mixture was then transferred to a reaction vessel. The molar ratio of silicon, ZrO, and (NH4)2HPO4 in the Mg / Al-SiOX@Gr material was 1:0.02:1.63. After solvothermal reaction (temperature 200℃, time 2 days), quenching, filtration, washing, and drying, a composite anode material (Zr(HPO4)2 coated Mg / Al-SiO) was obtained. X @Gr materials).

[0062] Example 2 This embodiment provides a composite anode material, whose modified silicon oxide core, and sequentially coated carbon material layer and zirconium-containing coating layer are consistent with those in Embodiment 1.

[0063] The preparation method of this composite anode material includes: S1. Carbon coating layer: Modified silicon oxide (Mg / Al-SiO2) x The modified silicon oxide, carbon material, and hydrazine hydrate solution were mixed, with a mass ratio of 28:70:2. The mixture was ultrasonically stirred and then transferred to a reactor for hydrothermal reaction (160℃ for 4 days). After cooling to room temperature, filtration, and washing, a graphene-coated composite material (Mg / Al-SiO₂) was obtained. X@Gr materials). The method for preparing modified silicon oxide includes: mixing silicon (average particle size approximately 100 nm), silicon dioxide (average particle size approximately 10 μm), aluminum-containing materials (containing aluminum and aluminum chloride in a molar ratio of 1:1), and magnesium-containing materials (containing magnesium and magnesium chloride in a molar ratio of 1:1), pressing them into spheres, and then feeding them into a vacuum furnace. The temperature inside the vacuum furnace is heated to 1000℃, and the vacuum degree inside the vacuum furnace is controlled at 30 Pa. A thermal reduction disproportionation reaction is carried out for 4 days to obtain modified silicon oxide (Mg / Al-SiOx material); wherein the molar ratio of magnesium in silicon, silicon dioxide, and magnesium-containing materials to aluminum in aluminum-containing materials is 1:1:0.5:0.5.

[0064] S2. Zirconium-containing coating: Mg / Al-SiO X The suspension of Mg / Al-SiOX@Gr material and ZrO powder dispersed in water was mixed with a (NH4)2HPO4 solution (a mixed solvent of water, isopropanol, and ethylene glycol), and ultrasonically stirred. The homogenized mixture was then transferred to a reaction vessel. The molar ratio of silicon, ZrO, and (NH4)2HPO4 in the Mg / Al-SiOX@Gr material was 1:0.02:1.63. After solvothermal reaction (at 170℃ for 4 days), quenching, filtration, washing, and drying, a composite anode material (Zr(HPO4)2 coated Mg / Al-SiO) was obtained. X @Gr materials).

[0065] Example 3 The composite anode material provided in this embodiment is basically the same as the composite anode material provided in Example 1. The difference is that in the modified silicon oxide, the ratio of the total molar number of magnesium and aluminum elements to the molar number of silicon elements is 0.08:1.

[0066] The preparation method of this composite anode material is basically the same as that of Example 1. The difference is that the molar ratio of silicon, silicon dioxide, magnesium in magnesium-containing materials and aluminum in aluminum-containing materials in the method of preparing modified silicon oxide is 1:1:0.08:0.08.

[0067] Example 4 The composite anode material provided in this embodiment is basically the same as the composite anode material provided in Example 1. The difference is that in the modified silicon oxide, the ratio of the total molar number of magnesium and aluminum elements to the molar number of silicon elements is 0.1:1.

[0068] The preparation method of this composite anode material is basically the same as that of Example 1, except that the molar ratio of silicon, silicon dioxide, magnesium in the magnesium-containing material, and aluminum in the aluminum-containing material is 1:1:0.1:0.1 in the method for preparing the modified silicon oxide. Example 5 The composite anode material provided in this embodiment is basically the same as the composite anode material provided in Example 1. The difference is that in the modified silicon oxide, the ratio of the total molar number of magnesium and aluminum elements to the molar number of silicon elements is 1:1.

[0069] The preparation method of this composite anode material is basically the same as that of Example 1, except that the molar ratio of silicon, silicon dioxide, magnesium in magnesium-containing materials, and aluminum in aluminum-containing materials is 1:1:1:1 in the method for preparing modified silicon oxide. Example 6 The composite anode material provided in this embodiment is basically the same as the composite anode material provided in Example 1. The difference is that in the modified silicon oxide, the ratio of the total molar number of magnesium and aluminum elements to the molar number of silicon elements is 1.2:1.

[0070] The preparation method of this composite anode material is basically the same as that of Example 1. The difference is that in the method of preparing modified silicon oxide, the molar ratio of silicon, silicon dioxide, magnesium element in magnesium-containing materials and aluminum element in aluminum-containing materials is 1:1:1.2:1.2.

[0071] Example 7 The composite anode material provided in this embodiment is basically the same as the composite anode material provided in Example 1. The difference is that in the modified silicon oxide, the molar ratio of magnesium to aluminum in the metal is 0.25:0.75 (i.e. 1:3).

[0072] The preparation method of this composite anode material is basically the same as that of Example 1. The difference is that in the method of preparing modified silicon oxide, the molar ratio of silicon, silicon dioxide, magnesium element in magnesium-containing materials and aluminum element in aluminum-containing materials is 1:1:0.25:0.75.

[0073] Example 8 The composite anode material provided in this embodiment is basically the same as the composite anode material provided in Example 1. The difference is that in the modified silicon oxide, the molar ratio of magnesium to aluminum in the metal is 0.5:1.

[0074] The preparation method of this composite anode material is basically the same as that of Example 1. The difference is that in the method of preparing modified silicon oxide, the molar ratio of silicon, silicon dioxide, magnesium element in magnesium-containing materials and aluminum element in aluminum-containing materials is 1:1:(1 / 3):(2 / 3).

[0075] Example 9 The composite anode material provided in this embodiment is basically the same as the composite anode material provided in Example 1, except that the molar ratio of magnesium to aluminum in the modified silicon oxide is 2:1.

[0076] The preparation method of this composite anode material is basically the same as that of Example 1. The difference is that in the method of preparing modified silicon oxide, the molar ratio of silicon, silicon dioxide, magnesium element in magnesium-containing materials and aluminum element in aluminum-containing materials is 1:1:(2 / 3):(1 / 3).

[0077] Example 10 The composite anode material provided in this embodiment is basically the same as the composite anode material provided in Example 1, except that the carbon content is 60.6%.

[0078] The preparation method of this composite anode material is basically the same as that of Example 1, except that the mass ratio of modified silicon oxide, carbon material and hydrazine hydrate is 28:60:2.

[0079] Example 11 The composite anode material provided in this embodiment is basically the same as the composite anode material provided in Example 1. The difference is that the molar ratio of zirconium element in the zirconium-containing coating layer (Zr(HPO4)2 layer) to silicon element in the modified silicon oxide is 0.01:1.

[0080] The preparation method of this composite anode material is basically the same as that of Example 1. The difference is that the molar ratio of silicon, ZrO and (NH4)2HPO4 in the Mg / Al-SiOX@Gr material in step S2 is 1:0.01:0.815.

[0081] Example 12 The composite anode material provided in this embodiment is basically the same as the composite anode material provided in Example 1. The difference is that the molar ratio of zirconium element in the zirconium-containing coating layer (Zr(HPO4)2 layer) to silicon element in the modified silicon oxide is 0.1:1.

[0082] The preparation method of this composite anode material is basically the same as that of Example 1. The difference is that the molar ratio of silicon, ZrO and (NH4)2HPO4 in the Mg / Al-SiOX@Gr material in step S2 is 1:0.1:8.15.

[0083] Example 13 The composite anode material provided in this embodiment is basically the same as the composite anode material provided in Example 1, except that the carbon material is carbon nanotubes.

[0084] The preparation method of this composite anode material is basically the same as that of Example 1, except that the graphene oxide dispersion is replaced with carbon nanotube dispersion in step S1.

[0085] Comparative Example 1 This comparative example provides a negative electrode material, which is silicon oxide.

[0086] The preparation method of this negative electrode material includes: Silicon (average particle size approximately 100 nm) and silicon dioxide (average particle size approximately 10 μm) were mixed with NaCl, granulated, and then fed into a vacuum furnace. The temperature inside the vacuum furnace was heated to 1200 °C, and the vacuum degree inside the vacuum furnace was controlled at 100 Pa. A thermal reduction disproportionation reaction was carried out for 2 days to obtain silicon oxide (SiOx material); wherein the molar ratio of silicon to silicon dioxide was 1:1.

[0087] Comparative Example 2 This comparative example provides a negative electrode material, which is a magnesium-doped modified silicon oxide, wherein the molar ratio of magnesium to silicon in the modified silicon oxide is 0.5:1.

[0088] The preparation method of this negative electrode material includes: Silicon (average particle size approximately 100 nm), silicon dioxide (average particle size approximately 10 μm), and magnesium-containing materials (containing magnesium and magnesium chloride in a molar ratio of 1:1) were mixed, granulated, and then fed into a vacuum furnace. The temperature inside the vacuum furnace was heated to 1200 °C, and the vacuum degree inside the vacuum furnace was controlled at 100 Pa. A thermal reduction disproportionation reaction was carried out for 2 days to obtain a composite anode material (Mg-SiOx material). The molar ratio of magnesium in silicon, silicon dioxide, and magnesium-containing materials was 1:1:1.

[0089] Comparative Example 3 This comparative example provides a negative electrode material, which is an aluminum-doped modified silicon oxide, wherein the molar ratio of aluminum to silicon in the modified silicon oxide is 0.5:1.

[0090] The preparation method of this negative electrode material includes: Silicon (average particle size approximately 100 nm), silicon dioxide (average particle size approximately 10 μm), and aluminum-containing materials (containing aluminum and aluminum chloride in a molar ratio of 1:1) were mixed, granulated, and then fed into a vacuum furnace. The temperature inside the vacuum furnace was heated to 1200 °C, and the vacuum degree inside the vacuum furnace was controlled at 100 Pa. A thermal reduction disproportionation reaction was carried out for 2 days to obtain a composite anode material (Al-SiOx material). The molar ratio of aluminum in silicon, silicon dioxide, and aluminum-containing materials was 1:1:1.

[0091] Comparative Example 4 This comparative example provides a negative electrode material, which is a magnesium-aluminum co-doped modified silicon oxide with a magnesium to aluminum molar ratio of 1:1 and a ratio of the total molar number of magnesium and aluminum to the molar number of silicon in the modified silicon oxide of 0.5:1.

[0092] The preparation method of this negative electrode material includes: Silicon (average particle size approximately 100 nm), silicon dioxide (average particle size approximately 10 μm), aluminum-containing materials (containing aluminum and aluminum chloride in a molar ratio of 1:1), and magnesium-containing materials (containing magnesium and magnesium chloride in a molar ratio of 1:1) were mixed, granulated, and then fed into a vacuum furnace. The temperature inside the vacuum furnace was heated to 1200 °C, and the vacuum degree inside the vacuum furnace was controlled at 100 Pa. A thermal reduction disproportionation reaction was carried out for 2 days to obtain a composite anode material (Mg / Al-SiOx material). The molar ratio of aluminum in silicon, silicon dioxide, and aluminum-containing materials to magnesium in magnesium-containing materials was 1:1:0.5:0.5.

[0093] Comparative Example 5 This comparative example provides a composite anode material, which consists only of a modified silicon oxide and a zirconium-containing coating layer from the inside out, without a carbon material (graphene) layer, and the modified silicon oxide and zirconium-containing coating layer are the same as in Example 1.

[0094] The preparation method of this composite anode material is basically the same as that in Example 1, except that the modified silicon oxide (Mg / Al-SiOx material) obtained in step S1 is used as the product of step S1, and is not coated with a carbon material layer; in step S2, the modified silicon oxide (Mg / Al-SiOx material) replaces Mg / Al-SiO. X @Gr materials.

[0095] Comparative Example 6 This comparative example provides a composite anode material, which consists only of a modified silicon oxide and carbon material layer from the inside out, without a zirconium-containing coating layer, and the modified silicon oxide and carbon material layer is the same as in Example 1.

[0096] The preparation method of this composite anode material is basically the same as that of Example 1, except that step S2 is omitted, and the composite material (Mg / Al-SiO2) coated with a graphene layer obtained in step S1 is used directly. X @Gr material) is used as the final composite anode material.

[0097] Comparative Example 7 This comparative example provides a composite anode material that is basically the same as that in Example 1, except that in the modified silicon oxide, the molar ratio of aluminum to silicon is 0.5:1, and magnesium is not doped.

[0098] The preparation method of this composite anode material is basically the same as that of Example 1. The difference is that in the method of preparing modified silicon oxide, the molar ratio of silicon, silicon dioxide and aluminum in aluminum-containing materials is 1:1:1, and no magnesium-containing materials are added.

[0099] Comparative Example 8 This comparative example provides a composite anode material that is basically the same as that in Example 1, except that the molar ratio of magnesium to silicon in the modified silicon oxide is 0.5:1, and aluminum is not doped.

[0100] The preparation method of this composite anode material is basically the same as that of Example 1. The difference is that in the method of preparing modified silicon oxide, the molar ratio of silicon, silicon dioxide and magnesium in magnesium-containing materials is 1:1:1, and no aluminum-containing materials are added.

[0101] Comparative Example 9 The composite anode material provided in Comparative Example 9 is basically the same as the composite anode material provided in Example 1, except that the carbon content is 80.8%.

[0102] The preparation method of this composite anode material is basically the same as that of Example 1, except that the mass ratio of modified silicon oxide, carbon material and hydrazine hydrate is 28:80:2.

[0103] Comparative Example 10 The composite anode material provided in Comparative Example 10 is basically the same as the composite anode material provided in Example 1, except that the molar ratio of zirconium element in the zirconium-containing coating layer (Zr(HPO4)2 layer) to silicon element in the modified silicon oxide is 0.2:1.

[0104] The preparation method of this composite anode material is basically the same as that of Example 1. The difference is that the molar ratio of silicon, ZrO and (NH4)2HPO4 in the Mg / Al-SiOX@Gr material in step S2 is 1:0.2:16.3.

[0105] The performance data of the composite anode material prepared in the embodiments and comparative examples of the present invention and the battery containing the composite anode material are shown in Table 1. The test methods for each performance data are as follows: Resistivity and conductivity: The four-probe method was used for testing. The specific testing method is as follows: (1) Preparation of negative electrode sheet: After drying the target negative electrode material, the target negative electrode material (90% by mass), binder (CMC, 5% by mass), and conductive agent (SP, 5% by mass) were mixed and coated on copper foil. The coated copper foil needs to be baked at 90°C for 4 hours, and then rolled and punched to make negative electrode sheet. (2) The resistance of the negative electrode sheet was tested using the four-probe method. (3) The resistivity and conductivity were calculated based on the resistance.

[0106] Cycle number: 4C rate fast charging (constant current and constant voltage charging), 1C constant current discharge, determine the cycle performance of the battery, and when the capacity retention rate is close to 80% (70%-87%), determine the cycle number. If the battery capacity jumps during the cycle, record the data of the cycle before the jump. The battery preparation process is as follows: (1) Preparation of negative electrode sheet: After drying the target negative electrode material, mix the target negative electrode material (90% by mass), binder (CMC, 5% by mass), and conductive agent (SP, 5% by mass) and coat it on copper foil; the coated copper foil needs to be baked at 90°C for 4 hours, and then rolled and punched to make negative electrode sheet; (2) Preparation of positive electrode sheet: mix the positive electrode material (NCM, 97% by mass), binder (PVDF, 1% by mass), and conductive agent (SP+CNT with a mass ratio of 3:1, total mass fraction 2%) and coat it on aluminum foil. The coated aluminum foil needs to be baked at 110°C for 4 hours, and then rolled and die-cut to form a positive electrode sheet (2) Assembly of the battery: The positive electrode sheet, fast charging electrolyte and negative electrode sheet are assembled into a soft pack battery by stacking in an environment with a dew point of <-30°C.

[0107] Specific capacity (1.5V) and initial charge / discharge efficiency (1.5V): (1) Preparation of negative electrode sheet: After drying the target negative electrode material, mix the target negative electrode material (90% by mass) with binder (CMC, 10% by mass) and coat it on copper foil; the coated copper foil needs to be baked at 90°C for 4 hours, and then rolled and punched to make a negative electrode sheet; (2) Assembly of battery: transfer the dried electrode sheet into the glove box, and use lithium sheet as positive electrode to assemble into a button cell. During the assembly process, it is necessary to ensure that the water and oxygen content in the glove box is less than 5ppm to ensure the sealing and stability of the battery; (3) Testing: The assembled button cell was tested using the LAND battery testing system. The voltage range of the test was 0.01V to 1.5V, and the charging and discharging mode was constant current / constant voltage charging and discharging mode (0.2C / 0.2C). (4) Calculate the specific capacity: By measuring the battery capacity (1.5V) and the mass of the active material, the specific capacity of the material can be calculated. Specific capacity = capacity / mass of active material. (5) Calculate the first charge and discharge efficiency: The first charge and discharge efficiency is calculated based on the first discharge capacity and the first charge capacity of 1.5V. First charge and discharge efficiency = (first discharge capacity / first charge capacity) × 100%.

[0108] Volume expansion rate: The total amount of gas generated during the battery cycle is calculated by measuring the volume of liquid that escapes, and then the volume expansion rate of the battery during the cycle is calculated. (1) Preparation stage: Put the battery into a sealed container, make sure the container is full of water, and the battery is completely submerged in the water. Record the weight of the battery relative to pure water m2. According to V0=m2 / ρ, the volume V0 of the battery before the test is obtained; (2) Test stage: Perform a cycle test on the battery (the battery preparation and test method are the same as the test of the number of cycles mentioned above). The battery will generate gas during the test. At the end of the cycle, record the weight of the battery relative to pure water m1. According to V1=m1 / ρ, the V1 of the battery after the test is obtained; (3) Calculate the gas production volume: According to V=V1-V0, calculate the gas production volume V; (5) Calculate the volume expansion rate of the battery, volume expansion rate = V / V0 (V0 is the volume of the battery before the test).

[0109] Table 1. Performance data of composite anode materials and batteries containing the composite anode materials of the embodiments and comparative examples of the present invention. It should be noted that in the table, 900 cycles @ 87% CR means that the capacity retention rate is 87% after 900 cycles, and so on.

[0110] As shown in Table 1, the composite anode material prepared in the embodiments of the present invention exhibits stable structure, small volume expansion, low resistivity, high conductivity, and good cycle stability. Batteries containing this composite anode material demonstrate high initial charge-discharge performance, excellent cycle life, and low volume expansion rate, with Example 1 showing the best overall performance. Examples 1 and 2 demonstrate that the preparation methods of this application can be used to prepare composite anode materials with excellent performance. Examples 1 and 3-6 show that by controlling the molar ratio of the doped metal element to silicon element, the structural stability and conductivity of the composite anode material can be effectively improved, resistivity reduced, and irreversible reactions of silicon oxide during initial lithium insertion to generate the byproduct Li2O can be avoided, thus preventing a decrease in initial charge-discharge performance. Furthermore, the volume expansion of the modified silicon oxide can be effectively suppressed, improving cycle stability. The improvement effect is more pronounced when the ratio of the two elements is controlled at 0.1~1:1 (Examples 1 and 4-5). As shown in Examples 1 and 7-9, by adjusting the molar ratio of magnesium and aluminum doping in the metal elements, the structural stability and conductivity of the composite anode material can be effectively improved, the resistivity reduced, and the irreversible reaction of silicon oxide during the first lithium insertion to generate the byproduct Li2O can be avoided, thus preventing a decrease in the first charge-discharge performance. Furthermore, the volume expansion of the modified silicon oxide can be effectively suppressed, improving cycle stability. The improvement is more pronounced when the ratio of magnesium to aluminum is controlled at 0.1~1:1 (Examples 1 and 8-9). In Example 7, the ratio of magnesium to aluminum was relatively high in one and relatively low in the other, affecting the functional groups. , The amount of carbon formed and its anchoring effect on the SiOx framework are relatively small, resulting in slightly inferior performance. As shown in Examples 1 and 10, controlling the mass fraction of carbon material within a suitable range can form a carbon material layer of appropriate thickness and uniform coating, thereby effectively improving the conductivity of the composite anode material, suppressing volume expansion, and reducing side reactions between silicon oxide and the cathode material, electrolyte, etc. As shown in Examples 1 and 11-12, by adjusting the molar ratio of silicon and zirconium, zirconium can form both CO bonds and Zr-O bonds, thereby improving the stability of the composite anode material, reducing side reactions between silicon oxide and the cathode material, electrolyte, etc., and also adsorbing solvated lithium ions, improving the lithium ion insertion efficiency in silicon oxide, further enhancing conductivity and cycle stability. As shown in Examples 1 and 13, the carbon material layers formed by various carbon materials all have good coating effects, effectively improving the conductivity of the composite anode material, effectively suppressing volume expansion, and reducing side reactions between silicon oxide and the cathode material, electrolyte, etc.

[0111] Compared to Example 1, the negative electrode material of Comparative Example 1 was unmodified silicon oxide, which had poor conductivity and poor cycle stability. Batteries containing this material exhibited low initial charge-discharge efficiency and high volume expansion. The negative electrode materials of Comparative Examples 2 and 3 were silicon oxides modified with Mg and Al, respectively. Although the introduction of metal elements can improve the conductivity of the modified silicon oxide core and stabilize the silicon oxide chain structure to some extent, since they are single-doped, only single Mg-O or Al-O bonds can be formed, and no functional groups can be formed. , Its anchoring effect on the SiOx framework is relatively weak, and its effect on increasing chain length is also relatively weak. During the first charge and discharge process (the first lithium insertion), a large amount of irreversible reaction will still occur, generating byproduct Li2O, which leads to the permanent loss of active lithium, resulting in poor first charge and discharge efficiency of the battery. In addition, the lack of synergistic effect between the carbon material layer and the zirconium-containing coating layer limits the improvement in conductivity. During the cycle charging process, there will still be a relatively serious structural collapse, severe volume expansion, and poor cycle stability. The negative electrode material of Comparative Example 4 was a silicon oxide modified with Mg / Al doping. Although the co-doping of magnesium and aluminum metal elements can improve the conductivity of the modified silicon oxide core to a certain extent, effectively stabilize the structure of the silicon oxide chain, and avoid irreversible reactions and the generation of by-product Li2O during the first charge and discharge process (first lithium insertion), the first charge and discharge efficiency is improved compared with the unmodified silicon oxide (Comparative Example 1). However, due to the lack of carbon material layer and zirconium-containing coating layer, the improvement in conductivity is limited. During the first charge and discharge process (first lithium insertion), a small amount of irreversible reaction still occurs, generating by-product Li2O, resulting in permanent loss of active lithium, which in turn leads to relatively poor first charge and discharge efficiency of the battery. During the cycle charging process, severe structural collapse, severe volume expansion, and poor cycle stability still occur. In Comparative Example 5, the negative electrode material directly uses a zirconium-containing coating layer (Zr(HPO4)2) to coat modified silicon oxide (Mg / Al-SiOx). Although this can improve the stability of the negative electrode material to a certain extent and reduce the reaction between silicon oxide and positive electrode material, electrolyte, etc., it lacks the synergistic effect of carbon material layer. The zirconium-containing coating layer cannot completely and effectively suppress the irreversible reaction during the first lithium insertion of the negative electrode material and the volume expansion during charge and discharge. In addition, the uniformity of the zirconium-containing coating layer formed by directly coating zirconium phosphate on silicon oxide is poor, the utilization rate of zirconium element is low, and the improvement of electronic conductivity is limited. It cannot effectively solve the problems of limited lithium-ion transport, volume expansion and poor cycle stability. Comparative Example 6 uses carbon-coated modified silicon oxide (Mg / Al-SiOx), which can suppress volume expansion to some extent and isolate the silicon-based anode material from the cathode material and electrolyte, etc. However, because the bonding network formed without zirconium doping is relatively weak, structural relaxation and phase separation are prone to occur. Therefore, the suppression effect on the irreversible reaction during the first lithium insertion of the silicon-based material and the volume expansion during battery charge and discharge is relatively poor. Furthermore, it cannot effectively prevent the contact and reaction between the silicon-based material and the cathode material and electrolyte during long-term charge and discharge, thus limiting the performance improvement. In addition, SiO... x During operation, it irreversibly decomposes into nano-silicon particles and a Li₂O / lithium silicate matrix. Without zirconium doping, the structure of these decomposition products is metastable, thus affecting the initial charge-discharge efficiency and cycle stability. In the negative electrode materials of Comparative Examples 7 and 8, the core is modified only by aluminum doping and magnesium doping, respectively, lacking the synergistic effect of another metal element, and thus unable to form functional groups. , The anchoring effect of the SiOx framework is weakened, and the increase in the chain length of the silicon-oxygen chain is limited, resulting in poorer cycle stability of the anode material, increased battery expansion rate, and relatively poor first charge-discharge performance. In Comparative Example 9, the anode material has an excessively high carbon content, forming an overly thick carbon coating layer that hinders volume expansion buffering. When silicon particles expand, they cannot effectively expand and instead crack, failing to provide protection and instead exacerbating local side reactions, thus limiting specific capacity and reducing the first charge-discharge efficiency (compared to Example 1), deteriorating later cycle stability. In Comparative Example 10, the anode material has an excessively high zirconium content, forming inert zirconium oxide clusters that disrupt ion / electron transport channels, blocking the transport paths of lithium ions and electrons within the material. This also increases the material's brittleness, leading to cracks and spalling in the anode material, reducing cycle stability and increasing the battery's volume expansion rate.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A composite negative electrode material, characterized by, The composite negative electrode material comprises, from inside to outside, a modified silicon oxide, a carbon material layer, and a zirconium-containing coating layer; the modified silicon oxide is a silicon oxide doped with a metal element; the metal element comprises magnesium and aluminum; the mass of the carbon material layer accounts for 60-72% of the mass of the composite negative electrode material; the zirconium-containing coating layer is a phosphate of nano-amorphous zirconium; and the molar ratio of zirconium element in the zirconium-containing coating layer to silicon element in the modified silicon oxide is 0.01-0.1:

1.

2. The composite negative material of claim 1, wherein, In the modified silicon oxide, the molar ratio of the metal element to silicon element is 0.1-1:1; and / or The molar ratio of magnesium to aluminum in the metal element is 0.5-2:

1.

3. The composite negative material of claim 1, wherein, The carbon material is at least one of carbon nanotubes and graphene; and / or The phosphate of zirconium is at least one of Zr(HPO4)2 and Zr(H2PO4)4, and is preferably Zr(HPO4)2.

4. A method for producing the composite negative electrode material according to any one of claims 1 to 3, characterized by, The preparation method comprises: S1. performing a hydrothermal reaction on a dispersion liquid containing the modified silicon oxide, a carbon source, and a reducing agent to form a carbon material layer on the surface of the modified silicon oxide, thereby obtaining a modified material; S2. performing a solvothermal reaction on a dispersion liquid containing the modified material, a zirconium source, and a phosphate source to form a zirconium-containing coating layer, thereby obtaining a composite negative electrode material.

5. The preparation method according to claim 4, characterized in that, In step S1, the mass ratio of the modified silicon oxide, the carbon source, and the reducing agent is 28-37:60-70:2-3; The carbon source is at least one of graphene oxide and carbon nanotubes; and / or The temperature of the hydrothermal reaction is 160-180°C, and the time is 2-4 days.

6. The preparation method according to claim 5, characterized in that, The reducing agent is hydrazine hydrate.

7. The preparation method according to claim 4, characterized in that, In step S2, the molar ratio of silicon element in the modified material to zirconium element in the zirconium source is 1:0.01-0.1; and / or The temperature of the solvothermal reaction is 170-200°C, and the time is 2-4 days.

8. The preparation method according to claim 7, characterized in that, The zirconium source is ZrO powder; the phosphate source is at least one of (NH4)2HPO4 and NH4H2PO4; and / or The solvent in the dispersion liquid comprises water and alcohol.

9. A battery, characterized by The battery is a liquid battery, a semi-solid battery, or a solid-state battery.

10. The battery of claim 9, wherein, ​

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