Carbon-coated positive electrode active material supplement material, and preparation method and application thereof

Abstract

A carbon-coated positive electrode active material supplementary material, its preparation method, and its application belong to the field of battery material technology. The carbon-coated positive electrode active material supplementary material of this invention has the following general chemical formula: G （4‑x） Z （x / n） Si （1‑y） B y O （4‑y / 2） @C, 0 < x < 4, 0 < y < 1, n equals the ionic valence of element Z, where G is the positive electrode active metal Li and / or Na, Z is at least one of the positive electrode active metal substituents Mg, Zn, Al, Co, Ti, and Nb, and C is a conductive carbon material. This invention, during battery charging, can release the positive electrode active metal to replenish the positive electrode active metal lost during SEI formation, improving coulombic efficiency and cycle life, thereby increasing battery energy density.

Description

Technical Field

[0001] This invention relates to a technology in the field of battery materials, specifically a carbon-coated positive electrode active material supplementary material, its preparation method, and its application. Background Technology

[0002] New energy batteries, especially lithium and sodium batteries, are widely used in power supplies, energy storage systems, and portable electronic devices due to their advantages such as high specific energy, long cycle life, and good safety. Compared to liquid batteries, solid-state batteries theoretically have higher energy density and better safety, making solid-state technology a research and development direction for future applications with higher requirements, such as power supplies, energy storage systems, and aircraft. However, both liquid and solid-state batteries form a solid electrolyte interface (SEI) at the negative electrode during the first cycle or subsequent operating cycles, resulting in irreversible capacity loss, reduced cycle life, and consequently, a decrease in battery energy density. This defect is generally compensated for by using lithium or sodium-based materials at the positive electrode.

[0003] Taking lithium-ion batteries as an example, common lithium replenishment materials include Li3N, Li2S, and Li4SiO4. Li3N has a theoretical specific capacity of 2309 mAh / g, and Li2S has a theoretical specific capacity of 1168 mAh / g. However, both are highly unstable in air, extremely sensitive to water and oxygen, and require very strict processing conditions, thus limiting large-scale production. Li4SiO4 has a high lithium extraction specific capacity and lower processing requirements as a lithium replenishment material; however, its poor conductivity means that adding it to the positive electrode active material can negatively impact battery performance.

[0004] The present invention is made to address the aforementioned problems existing in the prior art. Summary of the Invention

[0005] To address the aforementioned shortcomings of existing technologies, this invention proposes a carbon-coated positive electrode active material supplement, its preparation method, and its application. This supplement material can release positive electrode active metals during battery charging, replenishing the positive electrode active metals lost during SEI generation, thereby improving battery coulombic efficiency and cycle life, and ultimately increasing battery energy density.

[0006] The first aspect of this invention relates to a carbon-coated positive electrode active material supplement material, having the following general chemical formula:

[0007] G （4-x） Z （x / n） Si （1-y） B y O （4-y / 2） @C, 0 < x < 4, 0 < y < 1, n equals the ionic valence of element Z, where...

[0008] G is the positive electrode active metal Li and / or Na, Z is at least one of the positive electrode active metal substitution elements Mg, Zn, Al, Co, Ti and Nb; C is a conductive carbon material, and the mass of the conductive carbon material C accounts for 1% to 20% of the total mass of the carbon-coated positive electrode active material supplementary material.

[0009] The second aspect of this invention relates to a method for preparing the above-mentioned carbon-coated positive electrode active material supplementary material, comprising the following steps:

[0010] S1, silicon source, positive active metal source, boron source, positive active metal substitution element source and carbon source are added to solvent and mixed by sand milling, and then spray dried to prepare precursor;

[0011] S2, under a protective gas atmosphere, the precursor is sintered at 400-900℃ to obtain a positive electrode active material supplementary material coated with conductive carbon material; for example, the sintering temperature can be 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, etc., preferably, the sintering temperature is 750-850℃.

[0012] In some specific implementation schemes, the silicon source is at least one of elemental silicon, silicon suboxide, and silicon dioxide.

[0013] For some specific implementation schemes, the positive electrode active metal source includes a lithium source and / or a sodium source; further, the lithium source is at least one of lithium hydroxide, lithium carbonate, and lithium acetate; and the sodium source is at least one of sodium hydroxide, sodium carbonate, and sodium acetate.

[0014] For some specific implementation schemes, the boron source includes at least one of elemental boron, boron trioxide, boric acid, and lithium borate.

[0015] For some specific implementation schemes, the carbon source is at least one of citric acid, glucose, sucrose, polyethylene glycol, ascorbic acid, stearic acid, conductive carbon black, carbon nanotubes, carbon nanofibers, and graphene.

[0016] In some specific implementation schemes, the solvent is at least one of deionized water, ethanol, and acetone.

[0017] For some specific implementation schemes, the milling speed is 1000-4000 rpm, the time is 1-30 h, and the average particle size of the obtained precursor is no greater than 50 nm. For example, the milling speed is 1000 rpm, 1500 rpm, 2000 rpm, 2500 rpm, 3000 rpm, 3500 rpm, 4000 rpm, etc., and the milling time is 1 h, 5 h, 10 h, 20 h, 30 h, etc.

[0018] For some specific implementation schemes, the spray drying temperature is 60–150°C, and the resulting precursor particle size is 10 μm–30 μm. For example, the temperature is 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, etc., preferably 85–130°C.

[0019] In some specific implementations, the protective gas includes at least one of nitrogen and argon.

[0020] For some specific implementation schemes, the heating rate of the sintering treatment is 5-15℃ / min, and the holding time is 1-20h; for example, the heating rate is 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min, 11℃ / min, 12℃ / min, 13℃ / min, 14℃ / min, 15℃ / min, etc., and the holding time is 1h, 2h, 5h, 8h, 9h, 10h, 11h, 12h, 13h, 15h, 20h, etc.

[0021] The third aspect of this invention relates to the application of a carbon-coated positive electrode active material supplement in a battery, for example, in a positive electrode current collector, a positive electrode sheet, a positive electrode side separator, or a positive electrode side electrolyte membrane. The carbon-coated positive electrode active material supplement is added at a ratio of 1% to 10% of the mass of the positive electrode active material slurry. The battery is any one of a lithium battery, a sodium battery, or a lithium-sodium composite battery, and is not limited to liquid batteries, semi-solid batteries, or solid batteries.

[0022] When applied to the positive electrode current collector, a slurry made of carbon-coated positive electrode active material supplement is coated onto the surface of the positive electrode current collector and then dried and cured. The thickness of the cured coating is 1–20 μm. For example, the coating thickness is 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 15 μm, 20 μm, etc.

[0023] When applied to positive electrode sheets, carbon-coated positive electrode active material supplementary material is added to the positive electrode active material slurry, and then the positive electrode sheet is made according to the existing process system; or a slurry made of carbon-coated positive electrode active material supplementary material is coated on the surface of the positive electrode sheet and dried and cured. Preferably, the thickness of the cured coating is 1 to 20 μm.

[0024] When applied to the positive electrode side diaphragm, a slurry made of carbon-coated positive electrode active material supplement is coated on the surface of the positive electrode side diaphragm and then dried and cured; preferably, the thickness of the cured coating is 1 to 20 μm.

[0025] When applied to the positive electrode side electrolyte membrane, a slurry made of carbon-coated positive electrode active material supplement material is coated on the surface of the positive electrode side electrolyte membrane and then dried and cured; preferably, the thickness of the cured coating is 1 to 20 μm.

[0026] Compared with the prior art, the present invention has the following technical effects:

[0027] 1) The introduction of boron improves the stability of silicates; and the oxidation state of boron in the supplementary material is +3, which creates a vacancy at the oxygen position compared to silicon with a +4 oxidation state, thus improving the conductivity of the supplementary material.

[0028] 2) Introducing a substitution element. The substitution element has a higher oxidation state than lithium and sodium in the supplementary material. After substitution, it creates defects at the corresponding lithium and sodium positions, thereby improving the conductivity of the supplementary material.

[0029] 3) Sodium ions have a diameter of 1.02 Å, while lithium ions have a diameter of 0.76 Å, showing a significant difference in size. The supplementary material made by adding both lithium source and sodium-lithium can be applied to various batteries such as lithium batteries, sodium batteries, and lithium-sodium composite batteries. The introduction of sodium when adding lithium and the introduction of lithium when adding sodium increases the ion migration rate and improves the conductivity of the supplementary material.

[0030] 4) The carbon coating process inhibited the excessive growth of silicate grains during the synthesis of supplementary materials, shortening the Li... + / Na + The solid-phase diffusion path; at the same time, carbon materials, as electronic conductors, construct a three-dimensional conductive network, which makes up for the poor intrinsic electronic conductivity of silicates, and allows the electrochemical capacity of active materials to be fully utilized.

[0031] 5) The preparation method of the present invention is simple, the product yield is high, it is environmentally friendly, and it has good prospects for industrial application and is suitable for large-scale industrial production. Detailed Implementation

[0032] The present invention will now be described in detail with reference to specific embodiments. Experimental methods not specified in the embodiments were performed according to conventional methods and conditions.

[0033] Example 1

[0034] This embodiment aims to prepare a product with the chemical formula Li 3.75 Nb 0.05 Si 0.8 B 0.2 O 3.9 @C carbon-coated cathode lithium replenishment material.

[0035] 720.96g of SiO2, 1108.35g of Li2CO3, 1101.45g of LiOH·H2O, 104.43g of B2O3, 99.68g of Nb2O5, 236.77g of sucrose, 10.54g of SP, 10.54g of CNT and 14481g of deionized water were added to a sand mill and ground for 10 hours at a speed of 2500 r / min to obtain a slurry of nano-sized particles with a cumulative particle size distribution D97=28.8nm.

[0036] The slurry was spray-dried to form a precursor at a temperature of 85°C. The cumulative particle size distribution in the precursor was D97 = 17.6 μm.

[0037] The precursor was sintered by heating it to 750℃ at a rate of 5℃ / min under a nitrogen atmosphere and holding it at that temperature for 10 hours to obtain a carbon-coated positive electrode lithium replenishment material.

[0038] The prepared carbon-coated cathode lithium replenishment material was subjected to air jet milling to obtain carbon-coated cathode lithium replenishment material powder with cumulative particle size distribution D10=0.26μm, D50=1.2μm, and D90=3.8μm.

[0039] The positive electrode sheet was prepared by mixing carbon-coated positive electrode lithium supplement material powder, conductive agent SP, and binder PVDF5130 in a mass ratio of 90:6:4. The positive electrode sheet was baked in a vacuum oven at 80°C for 10 hours and dynamically dried by N2 replacement once every 2 hours. The dried positive electrode sheet was then used to fabricate 2032 coin cells in an argon atmosphere glove box.

[0040] Electrochemical tests were conducted on the 2032 coin cell at a current density of 0.1C, and the initial charge specific capacity of the cell was measured to be 771.6 mAh / g, demonstrating the excellent performance of the carbon-coated cathode lithium replenishment material.

[0041] Example 2

[0042] This embodiment aims to prepare a product with the chemical formula Li 3.75 Nb 0.05 Si 0.7 B 0.3 O 3.85 @C carbon-coated cathode lithium replenishment material.

[0043] 630.84g of SiO2, 1108.35g of Li2CO3, 1101.45g of LiOH·H2O, 156.65g of B2O3, 99.68g of Nb2O5, 232.29g of sucrose, 10.34g of SP, 10.34g of CNT and 14481g of deionized water were added to a sand mill and ground for 10 hours at a speed of 2500 r / min to obtain a nano-sized particle slurry with a cumulative particle size distribution D97=30nm.

[0044] The slurry was spray-dried to form a precursor at a temperature of 125℃. The cumulative particle size distribution in the precursor was D97 = 19.6 μm.

[0045] The precursor was sintered under nitrogen atmosphere by heating it to 750℃ at 5℃ / min and holding it for 10h to obtain carbon-coated positive electrode lithium replenishment material.

[0046] The prepared carbon-coated cathode lithium replenishment material was subjected to air jet milling to obtain carbon-coated cathode lithium replenishment material powder with cumulative particle size distribution D10=0.3μm, D50=1.0μm, and D90=5μm.

[0047] The positive electrode sheet was prepared by mixing carbon-coated positive electrode lithium supplement material powder, conductive agent SP, and binder PVDF5130 in a mass ratio of 90:6:4. The positive electrode sheet was baked in a vacuum oven at 80°C for 10 hours and dynamically dried by N2 replacement once every 2 hours. The dried positive electrode sheet was then used to fabricate 2032 coin cells in an argon atmosphere glove box.

[0048] Electrochemical tests were performed on the 2032 coin cell at a current density of 0.1C, and the initial charge specific capacity of the cell was measured to be 787.5 mAh / g.

[0049] Example 3

[0050] This embodiment aims to prepare a product with the chemical formula Li 3.75 Mg 0.125 Si 0.9 B 0.1 O 3.95 @C carbon-coated cathode lithium replenishment material.

[0051] 811.08g of SiO2, 1108.35g of Li2CO3, 1101.45g of LiOH·H2O, 52.22g of B2O3, 75.57g of MgO, 238.39g of sucrose, 10.61g of SP, 10.61g of CNT and 14481g of deionized water were added to a sand mill and ground for 10 hours at a speed of 2500 r / min to obtain a slurry of nano-sized particles with a cumulative particle size distribution D97=29.2nm.

[0052] The slurry was spray-dried to form a precursor at a temperature of 130℃. The cumulative particle size distribution in the precursor was D97 = 21.9 μm.

[0053] The precursor was sintered by heating it to 780℃ at 5℃ / min under nitrogen atmosphere and holding it for 10h to obtain carbon-coated positive electrode lithium replenishment material.

[0054] The prepared carbon-coated cathode lithium supplement material was subjected to air jet milling to obtain a cumulative particle size distribution of D10=0.25μm, D50=1.24μm, and D90=4.06μm.

[0055] The positive electrode sheet was prepared by mixing carbon-coated positive electrode lithium supplement material powder, conductive agent SP, and binder PVDF5130 in a mass ratio of 90:6:4. The positive electrode sheet was baked in a vacuum oven at 80°C for 10 hours and dynamically dried by N2 replacement once every 2 hours. The dried positive electrode sheet was then used to fabricate 2032 coin cells in an argon atmosphere glove box.

[0056] Electrochemical tests were performed on the 2032 coin cell at a current density of 0.1C, and the initial charge specific capacity of the cell was measured to be 764.6 mAh / g.

[0057] Example 4

[0058] This embodiment aims to prepare a product with the chemical formula Li 3.75 Al 1 / 12 Si 0.7 B 0.3 O 3.85 @C carbon-coated cathode lithium replenishment material.

[0059] 630.84g of SiO2, 1108.35g of Li2CO3, 1101.45g of LiOH·H2O, 63.78g of Al2O3, 156.65g of B2O3, 228.04g of sucrose, 10.15g of SP, 10.15g of CNT and 14481g of deionized water were added to a sand mill and ground for 10 hours at a speed of 2500 r / min to obtain a nano-sized particle slurry with a cumulative particle size distribution D97=32nm.

[0060] The slurry was spray-dried to form a precursor at a temperature of 130℃. The cumulative particle size distribution in the precursor was D97 = 23.9 μm.

[0061] The precursor was sintered under nitrogen atmosphere by heating it to 850℃ at 5℃ / min and holding it at that temperature for 8h to obtain carbon-coated positive electrode lithium replenishment material.

[0062] The prepared carbon-coated cathode lithium replenishment material was subjected to air jet milling to obtain a cumulative particle size distribution of D10=0.35μm, D50=1.34μm, and D90=6.06μm.

[0063] The positive electrode sheet was prepared by mixing carbon-coated positive electrode lithium supplement material powder, conductive agent SP, and binder PVDF5130 in a mass ratio of 90:6:4. The positive electrode sheet was baked in a vacuum oven at 80°C for 10 hours and dynamically dried by N2 replacement once every 2 hours. The dried positive electrode sheet was then used to fabricate 2032 coin cells in an argon atmosphere glove box.

[0064] Electrochemical tests were performed on the 2032 coin cell at a current density of 0.1C, and the initial charge specific capacity of the cell was measured to be 804.3 mAh / g.

[0065] Example 5

[0066] This embodiment aims to prepare a product with the chemical formula Li 2.81 Na 0.94 Nb 0.05 Si 0.8 B 0.2 O 3.9 @C carbon-coated cathode lithium replenishment material.

[0067] 720.96g of SiO2, 1108.35g of Li2CO3, 509.81g of LiOH·H2O, 747.23g of Na2CO3, 104.43g of B2O3, 99.68g of Nb2O5, 218.50g of sucrose, 9.72g of SP, 9.72g of CNT, and 14481g of deionized water were added to a sand mill and ground for 10 hours at a speed of 2500 r / min to obtain a nano-sized particle slurry with a cumulative particle size distribution D97=29.5nm.

[0068] The slurry was spray-dried to form a precursor at a temperature of 85°C. The cumulative particle size distribution in the precursor was D97 = 18.2 μm.

[0069] The precursor was sintered under nitrogen atmosphere by heating it to 750℃ at 5℃ / min and holding it for 10h to obtain carbon-coated positive electrode lithium replenishment material.

[0070] The prepared carbon-coated cathode lithium replenishment material was subjected to air jet milling to obtain a cumulative particle size distribution of D10=0.28μm, D50=1.15μm, and D90=3.9μm.

[0071] The positive electrode sheet was prepared by mixing carbon-coated positive electrode lithium supplement material powder, conductive agent SP, and binder PVDF5130 in a mass ratio of 90:6:4. The positive electrode sheet was baked in a vacuum oven at 80°C for 10 hours and dynamically dried by N2 replacement once every 2 hours. The dried positive electrode sheet was then used to fabricate 2032 coin cells in an argon atmosphere glove box.

[0072] Electrochemical tests were performed on the 2032 coin cell at a current density of 0.1C, and the initial charge specific capacity of the cell was measured to be 683.3 mAh / g.

[0073] Comparative Example 1

[0074] This comparative example aims to prepare a carbon-coated cathode lithium replenishment material with the chemical formula Li4SiO4@C.

[0075] 901.2g of SiO2, 1773.36g of Li2CO3, 503.52g of LiOH·H2O, 225g of sucrose, 10.03g of SP, 10.03g of CNT and 14481g of deionized water were added to a sand mill and ground for 10 hours at a speed of 2500 r / min to obtain a nano-sized particle slurry with a cumulative particle size distribution D97=29.8nm.

[0076] The slurry was spray-dried to form a precursor at a temperature of 125°C. The cumulative particle size distribution in the precursor was D97 = 17.6 μm.

[0077] The precursor was sintered under nitrogen atmosphere by heating it to 750℃ at 5℃ / min and holding it for 10h to obtain carbon-coated positive electrode lithium replenishment material.

[0078] The prepared carbon-coated cathode lithium replenishment material was subjected to air jet milling to obtain a cumulative particle size distribution of D10=0.36μm, D50=2.2μm, and D90=5.8μm.

[0079] The positive electrode sheet was prepared by mixing carbon-coated positive electrode lithium supplement material powder, conductive agent SP, and binder PVDF5130 in a mass ratio of 90:6:4. The positive electrode sheet was baked in a vacuum oven at 80°C for 10 hours and dynamically dried by N2 replacement once every 2 hours. The dried positive electrode sheet was then used to fabricate 2032 coin cells in an argon atmosphere glove box.

[0080] Electrochemical tests were performed on the 2032 coin cell at a current density of 0.1C, and the initial charge specific capacity of the cell was measured to be 198.6 mAh / g.

[0081] Comparative Example 2

[0082] This comparative example aims to prepare a product with the chemical formula Li 3.75 Nb 0.05Si 0.8 B 0.2 O 3.9 The positive electrode lithium replenishment material.

[0083] 720.96g of SiO2, 1108.35g of Li2CO3, 1101.45g of LiOH·H2O, 104.43g of B2O3, 99.68g of Nb2O5 and 14481g of deionized water were added to a sand mill and ground for 10 hours at a speed of 2500 r / min to obtain a slurry of nano-sized particles with a cumulative particle size distribution D97=28.5nm.

[0084] The slurry was spray-dried to form a precursor at a temperature of 130℃. The cumulative particle size distribution in the precursor was D97 = 18.2 μm.

[0085] The precursor was sintered under nitrogen atmosphere by heating to 780℃ at 5℃ / min and holding for 10h to obtain positive electrode lithium supplementation material powder.

[0086] The prepared positive electrode lithium replenishment material was subjected to air jet milling to obtain a cumulative particle size distribution of D10=0.42μm, D50=1.8μm, and D90=5.2μm.

[0087] The positive electrode sheet was prepared by mixing positive electrode lithium supplement material powder, conductive agent SP, and binder PVDF5130 in a mass ratio of 90:6:4. The positive electrode sheet was baked in a vacuum oven at 80°C for 10 hours and dynamically dried by N2 replacement once every 2 hours. The dried positive electrode sheet was then used to manufacture 2032 coin cells in an argon atmosphere glove box.

[0088] Electrochemical tests were performed on the 2032 coin cell at a current density of 0.1C, and the initial charge specific capacity of the cell was measured to be 485.3 mAh / g.

[0089] Comparative Example 3

[0090] This comparative example aims to prepare a product with the chemical formula Li4Si. 0.8 B 0.2 O 3.9 @C carbon-coated cathode lithium replenishment material.

[0091] 720.96g of SiO2, 1108.35g of Li2CO3, 1258.8g of LiOH·H2O, 104.43g of B2O3, 235.57g of sucrose, 10.48g of SP, 10.48g of CNT and 14481g of deionized water were added to a sand mill and ground for 10 hours at a speed of 2500 r / min to obtain a nano-sized particle slurry with a cumulative particle size distribution D97=29.5nm.

[0092] The slurry was spray-dried to form a precursor at a temperature of 130℃. The cumulative particle size distribution in the precursor was D97 = 17.9 μm.

[0093] The precursor was sintered by heating it to 780℃ at 5℃ / min under nitrogen atmosphere and holding it for 10h to obtain carbon-coated positive electrode lithium replenishment material.

[0094] The prepared carbon-coated cathode lithium replenishment material was subjected to air jet milling to obtain a cumulative particle size distribution of D10=0.45μm, D50=1.54μm, and D90=4.9μm.

[0095] The positive electrode sheet was prepared by mixing carbon-coated positive electrode lithium supplement material powder, conductive agent SP, and binder PVDF5130 in a mass ratio of 90:6:4. The positive electrode sheet was baked in a vacuum oven at 80°C for 10 hours and dynamically dried by N2 replacement once every 2 hours. The dried positive electrode sheet was then used to fabricate 2032 coin cells in an argon atmosphere glove box.

[0096] Electrochemical tests were conducted on the 2032 coin cell at a current density of 0.1C, and the initial charge specific capacity was measured to be 512.4 mAh / g. Compared with Example 4, since no substitution elements were introduced and no sodium was doped, the conductivity of the lithium-filling material showed a significant decrease.

[0097] Comparative Example 4

[0098] This comparative example aims to prepare a product with the chemical formula Li 3.75 Nb 0.05 SiO4@C carbon-coated cathode lithium replenishment material.

[0099] 901.2g of SiO2, 1108.35g of Li2CO3, 1101.45g of LiOH·H2O, 99.68g of Nb2O5, 245.74g of sucrose, 10.94g of SP, 10.94g of CNT and 14481g of deionized water were added to a sand mill and ground for 10 hours at a speed of 2500 r / min to obtain a nano-sized particle slurry with a cumulative particle size distribution D97=30.1nm.

[0100] The slurry was spray-dried to form a precursor at a temperature of 80°C. The cumulative particle size distribution in the precursor was D97 = 22.5 μm.

[0101] The precursor was sintered under nitrogen atmosphere by heating it to 750℃ at 5℃ / min and holding it for 10h to obtain carbon-coated positive electrode lithium replenishment material.

[0102] The prepared carbon-coated cathode lithium replenishment material was subjected to air jet milling to obtain a cumulative particle size distribution of D10=0.35μm, D50=1.6μm, and D90=4.06μm.

[0103] The positive electrode sheet was prepared by mixing carbon-coated positive electrode lithium supplement material powder, conductive agent SP, and binder PVDF5130 in a mass ratio of 90:6:4. The positive electrode sheet was baked in a vacuum oven at 80°C for 10 hours and dynamically dried by N2 replacement once every 2 hours. The dried positive electrode sheet was then used to fabricate 2032 coin cells in an argon atmosphere glove box.

[0104] Electrochemical tests were performed on the 2032 coin cell at a current density of 0.1C, and the initial charge specific capacity was measured to be 498.7 mAh / g. Compared with Example 1, no boron was introduced in this comparative example, resulting in a significant decrease in the conductivity of the lithium-supplementing material.

[0105] test

[0106] As shown in Table 1 below, the carbon-coated positive electrode active material supplementary materials prepared in Examples 1-5 and Comparative Examples 1-4 were added to the positive electrode to prepare 2032 coin cells, which were then tested. The test voltage window for the NCM811 positive electrode was 3.0–4.3V; the test voltage window for the LFP positive electrode was 2.5–3.7V; and the test voltage window for the NFPP positive electrode was 2.0–3.8V.

[0107] The test results are as follows:

[0108] Table 1 Battery Parameter Performance Table 1 LFP graphite Example 1 Added to the positive electrode active material slurry to form a positive electrode sheet 3% 180.4 150.9 97.5% 2 NCM811 graphite Example 1 Coated onto the surface of the positive electrode current collector 5% 243.3 189.7 92.5% 3 LFP graphite Example 2 Added to the positive electrode active material slurry to form a positive electrode sheet 3% 179.5 148.3 97.0% 4 NCM811 graphite Example 2 Coated to the positive electrode side diaphragm 5% 239.1 188.8 91.2% 5 LFP graphite Example 3 Added to the positive electrode active material slurry to form a positive electrode sheet 3% 179.5 149.4 90.0% 6 NCM811 graphite Example 4 Coated onto the surface of the positive electrode 5% 248.7 188.9 91.0% 7 LFP graphite Example 5 Added to the positive electrode active material slurry to form a positive electrode sheet 3% 179.3 150.8 97.4% 8 NFPP Hard carbon Example 5 Added to the positive electrode active material slurry to form a positive electrode sheet 3% 136.2 105.3 94.5% 9 LFP graphite Comparative Example 1 Added to the positive electrode active material slurry to form a positive electrode sheet 3% 164.1 148.2 88.4% 10 NCM811 graphite Comparative Example 2 Coated onto the surface of the positive electrode current collector 5% 228.6 187.1 86.1% 11 LFP graphite Comparative Example 3 Added to the positive electrode active material slurry to form a positive electrode sheet 3% 171.8 149.6 85.2% 12 NCM811 graphite Comparative Example 4 Coated onto the surface of the positive electrode 5% 228.5 188.3 86.1%

[0109] Based on the experimental data in Table 1, regardless of whether the lithium replenishment material of the present invention is introduced into the positive electrode sheet, the positive electrode current collector, or the positive electrode side separator, compared with the addition of conventional high silicate (comparative) lithium replenishment, the first-cycle charge-discharge specific capacity and the coulombic efficiency after 500 cycles are significantly improved.

[0110] It should be emphasized that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A carbon-coated positive electrode active material supplement material, characterized in that, It has the following general chemical formula: G （4-x） Z （x / n） Si （1-y） B y O （4-y / 2） @C, 0 < x < 4, 0 < y < 1, n equals the ionic valence of element Z, where... G is the positive electrode active metal Li and / or Na, Z is at least one of the positive electrode active metal substitution elements Mg, Zn, Al, Co, Ti and Nb; C is a conductive carbon material, and the mass of the conductive carbon material C accounts for 1% to 20% of the total mass of the carbon-coated positive electrode active material supplementary material.

2. A method for preparing a carbon-coated positive electrode active material supplementary material as described in claim 1, characterized in that, Includes the following steps: S1, silicon source, positive active metal source, boron source, positive active metal substitution element source and carbon source are added to solvent and mixed by sand milling, and then spray dried to prepare precursor; S2, under a protective gas atmosphere, the precursor is sintered at 400-900℃ to obtain a positive electrode active material supplementary material coated with conductive carbon material.

3. The preparation method according to claim 2, characterized in that, The silicon source is at least one of elemental silicon, silicon suboxide, and silicon dioxide; The positive electrode active metal source includes a lithium source and / or a sodium source; further, the lithium source is at least one of lithium hydroxide, lithium carbonate, and lithium acetate; the sodium source is at least one of sodium hydroxide, sodium carbonate, and sodium acetate. The boron source includes at least one of elemental boron, boron trioxide, boric acid, and lithium borate; The carbon source is at least one of citric acid, glucose, sucrose, polyethylene glycol, ascorbic acid, stearic acid, conductive carbon black, carbon nanotubes, carbon nanofibers, and graphene. The solvent is at least one of deionized water, ethanol, and acetone.

4. The preparation method according to claim 2, characterized in that, The grinding and mixing speed is 1000-4000 rpm, and the time is 1-30 h, so that the average particle size of the precursor is not greater than 50 nm.

5. The preparation method according to claim 2, characterized in that, The spray drying temperature is 60–150°C.

6. The preparation method according to claim 2, characterized in that, The protective gas includes at least one of nitrogen and argon.

7. The preparation method according to claim 2, characterized in that, The heating rate of the sintering process is 5–15 °C / min, and the holding time is 1–20 h.

8. A battery, characterized in that, The battery contains at least one of the positive electrode current collector, positive electrode sheet, positive electrode side separator, and positive electrode side electrolyte membrane as described in claim 1, which contains a carbon-coated positive electrode active material supplementary material.

9. The battery according to claim 8, characterized in that, The carbon-coated positive electrode active material supplementary material is added at a ratio of 1% to 10% of the mass of the positive electrode active material slurry.