CN114497452A - Positive electrode material for silicon battery and preparation method and application thereof - Google Patents

Abstract

The invention provides a positive electrode material for a silicon battery, a preparation method and application thereof, wherein the chemical formula of the positive electrode material is Li_1+aNi_bMn_cM_c‑dO₂Wherein a is more than or equal to 0 and less than or equal to 1, b is more than 0 and less than 1, c is more than 0 and less than 1, d is more than or equal to c, and b +2c-d is less than 1+ a; m is at least one of Ti, Zr, La, Ce, Pr, Nd, Nb, Sm, Al, Mg, Sr, Ba, Co, Zn, Sn, Bi, Sb, Si, Tb, Bi, Yb, Lu, B and Y. Compared with the prior art, the positive electrode material provided by the invention carries a part of lithium, can be used for generating lithium which needs to be consumed by an SEI (solid electrolyte interface) film in the first charging process of a silicon negative electrode material, and solves the problems that the prior silicon lithium ion battery needs to be pre-lithiated in advance and has high production costThe matching with the silicon-based anode material is higher.

Description

Cathode material for silicon-based battery, preparation method and application thereof

technical field

The invention relates to the field of lithium batteries, in particular to a positive electrode material for silicon-based batteries and a preparation method and application thereof.

Background technique

Lithium-ion battery is a very widely used secondary battery. With the pursuit of high energy density of lithium-ion battery, especially for power battery to achieve the specific energy target of 300Wh/kg, the negative electrode material must be silicon-based (nanometer). silicon or silicon oxide, etc.) negative electrode. However, silicon-based anode materials have a fatal problem. When the lithium intercalation reaction is performed for the first time, a solid electrolyte film (SEI film) will be formed, and a part of lithium will be consumed in this process. When the conventional positive electrode material is matched with the silicon-based negative electrode, a large amount of active lithium released from the positive electrode material during the first charging process will become dead lithium and be trapped in the SEI film of the silicon-based negative electrode, which will greatly reduce the actual specific energy of the battery.

In order to solve this problem, lithium is supplemented by pre-lithiation in the silicon-based negative electrode lithium-ion battery to make up for the lithium consumed by the silicon-based negative electrode to generate the SEI film. There are two prelithiation methods that have been reported so far, lithium supplementation at the positive end or lithium supplementation at the negative end.

The conventional cathode electrode lithium supplementation technology mainly adds some compounds with high lithium content and can be extracted, such as Li ₂ O, Li ₂ NiO ₂ and Li ₅ FeO ₄ , during the preparation of the cathode electrode slurry. Such compounds with high lithium content are generally sensitive to moisture in the air, so there are strict requirements for moisture control in the slurry preparation environment and the electrode coating environment. The humidity environment of the existing battery production line needs to be upgraded, and the transformation cost is high.

Conventional negative electrode lithium replenishment technology generally uses lithium foil, lithium tape, metal lithium powder, etc., combined with the preparation process of the negative electrode pole piece to achieve lithium replenishment. Lithium foil, lithium strip, metal lithium powder, etc. are relatively active, and have strict requirements on environmental humidity and atmosphere, and are prone to safety accidents such as fire or explosion if they are not careful. Therefore, higher requirements are placed on the equipment and environment of the battery production workshop.

The above two types of lithium replenishment methods are more technically difficult for lithium-ion battery manufacturers, existing production equipment needs to be improved or upgraded, and production costs increase.

In view of this, it is indeed necessary to provide a technical solution to solve the above problems.

SUMMARY OF THE INVENTION

One of the objectives of the present invention is to provide a positive electrode material for a silicon-based battery, so as to solve the problems of high technical difficulty and high production cost of pre-lithiation in the current silicon-based lithium ion battery. Lithium-ion batteries not only do not require additional lithium supplementation, but also have low production costs, high capacity, and higher matching with silicon anodes.

In order to achieve the above object, the present invention adopts the following technical solutions:

A positive electrode material for a silicon-based battery, the chemical formula is Li _1+a Ni _b Mn _c M _cd O ₂ , wherein 0≤a≤1, 0<b<1, 0<c<1, 0<d<1 , and d≤c, b+2c-d<1+a; M is Ti, Zr, La, Ce, Pr, Nd, Nb, Sm, Al, Mg, Sr, Ba, Co, Zn, Sn, Bi, At least one of Sb, Si, Tb, Bi, Yb, Lu, B, and Y.

Another object of the present invention is to provide a method for preparing the above-mentioned positive electrode material for a silicon-based battery, comprising the following steps:

S1, the nickel salt and the manganese salt are mixed to prepare the first solution, in the inert gas, the first solution and the alkaline solution are respectively added to the reactor for stirring reaction, and the pH of the control solution is 7～13; Continue to stir after feeding 18 ~ 26h, vacuum filtration, washing, drying to obtain the precursor;

S2, mixing the precursor obtained in step S1 with the lithium salt and putting it into a reaction furnace, reacting at 450-900° C. for 8-30 hours, cooling and grinding to obtain a positive electrode material for silicon-based batteries;

Wherein, M salt is mixed with nickel salt and manganese salt in step S1 to prepare the first solution, or in step S2, it is mixed with the precursor and lithium salt obtained in step S1 for reaction.

Preferably, the lithium salt is at least one of lithium oxide, lithium carbonate, lithium nitrate, lithium acetate and lithium hydroxide; the nickel salt is nickel nitrate, nickel at least one of manganese carbonate, nickel oxalate, nickel acetate and nickel oxide; the manganese salt is at least one of manganese nitrate, manganese carbonate, manganese oxalate, manganese acetate and manganese oxide; The M salt is at least one of M nitrate, M carbonate, M acetate, M hydroxide and M oxide.

Preferably, nickel, manganese, and M in the nickel salt, manganese salt, and M salt are denoted as metal A, and the molar ratio of the metal A to the lithium in the lithium salt is 1:(1.05-1.5).

Preferably, in step S1, the preparation method of the precursor is as follows: a first solution is prepared by mixing nickel salt, manganese salt and M salt, and the first solution is mixed with an alkaline solution in an inert gas at 30-80° C. Add to the reactor with deionized water at a speed of 0.8-1.2mL/min and stir the reaction, the stirring speed is 400-600rpm/min, and the pH of the solution is controlled to be 7-13; after feeding, continue to stir and age for 18- 26h, vacuum filtration, washing, drying at 100-120°C for 40-60h to obtain the precursor.

Preferably, in step S2, the lithium salt is firstly divided into a first part and a second part, the first part of the lithium salt is mixed with the precursor, reacted at 450-900° C. for 8-24 hours, cooled and ground; and then added The second part of the lithium salt is mixed together, reacted at 450-900° C. for 8-24 hours, cooled and ground to obtain a positive electrode material for a silicon-based battery.

Preferably, the mass ratio of the first part of the lithium salt to the second part of the lithium salt is (5-9): (5-1).

Preferably, in step S2, the first part of the lithium salt is mixed with the precursor, and the temperature is first heated to 450-650°C at a rate of 4-7°C/min, kept for 1-3 hours, and then heated to 4-7°C/min at a rate of 4-7°C/min. The temperature is raised to 700～900℃ at a rate of 700～900℃, kept for 10～24h, then cooled and ground; then the second part of lithium salt is added and mixed together, and the temperature is raised to 450～650℃ at a rate of 4～7℃/min, and the temperature is kept for 1～3h. Then, the temperature is raised to 700-900° C. at a rate of 4-7° C./min, maintained for 10-24 hours, cooled, and ground to obtain a positive electrode material for a silicon-based battery.

The third object of the present invention is to provide a positive electrode sheet, comprising a positive electrode current collector and a positive electrode active material layer coated on at least one surface of the positive electrode current collector, the positive electrode active material layer comprising the above-mentioned silicon-based battery Use positive electrode material.

The fourth object of the present invention is to provide a lithium ion battery, comprising a positive electrode sheet, a negative electrode sheet, and a separator spaced between the positive electrode sheet and the negative electrode sheet, and the negative electrode active material in the negative electrode sheet is silicon-based material, the positive electrode sheet is the above-mentioned positive electrode sheet.

Compared with the prior art, the beneficial effects of the present invention are:

1) The positive electrode material for a silicon-based lithium-ion battery provided by the present invention, the positive electrode material itself has a part of lithium, which cannot be re-inserted into the material after the first extraction (corresponding to the first charging process), so it is different from the silicon-based negative electrode material. Used together, it can be used for the lithium consumed by the silicon-based negative electrode material to generate the SEI film during the first charging process. Compared with other positive electrode materials and silicon-based negative electrode materials, a pre-lithiation process must be added. The positive electrode material of the present invention avoids The process of adding lithium supplementary agent additionally reduces the process complexity and production difficulty of the battery production process, thereby solving the current problems of pre-lithiation and high production cost of silicon-based lithium-ion batteries. match higher.

2) In addition, the positive electrode material provided by the present invention itself has a high mass specific capacity, even if the lithium ion is charged and released for the first time for the silicon-based negative electrode to form an SEI film, it can still match the high-capacity silicon-carbon negative electrode and provide a higher mass ratio. capacity.

3) In addition, the preparation method provided by the present invention can effectively adjust the surplus lithium amount in the positive electrode material for silicon-based batteries (for silicon-carbon negative electrode to form SEI film) and the effective mass specific capacity (mass ratio that can be recovered after the first discharge). capacity) to match different types of silicon-based anode materials.

Description of drawings

FIG. 1 is an XRD pattern of a positive electrode material for a silicon-based battery in Example 1 of the present invention.

FIG. 2 is an XRD pattern of a positive electrode material for a silicon-based battery in Example 2 of the present invention.

3 is an XRD pattern of a positive electrode material for a silicon-based battery in Example 3 of the present invention.

4 is an XRD pattern of the positive electrode material for a silicon-based battery in Example 6 of the present invention.

5 is an XRD pattern of the positive electrode material for a silicon-based battery in Example 9 of the present invention.

Detailed ways

1. Cathode materials for silicon batteries

A first aspect of the present invention provides a positive electrode material for a silicon-based battery, the chemical formula of which is Li _1+a Ni _b Mn _c M _cd O ₂ , wherein 0≤a≤1, 0<b<1, 0<c< 1, 0<d<1, and d≤c, b+2c-d<1+a; M is Ti, Zr, La, Ce, Pr, Nd, Nb, Sm, Al, Mg, Sr, Ba, Co , at least one of Zn, Sn, Bi, Sb, Si, Tb, Bi, Yb, Lu, B, Y.

Specifically, the positive electrode material for a silicon-based battery of the present invention includes but is not limited to

Li _1.05 Ni _0.8 Mn _0.1 Co _0.05 Al _0.05 O ₂ , Li _1.05 Ni _0.8 Mn _0.1 Co _{0.05 Mg 0.05} O ₂ , Li _1.05 Ni _0.8 Mn _0.1 Co _0.05 Ti _0.05 O ₂ , Li _1.05 Ni _0.6 Mn _0.35 Co _0.0 Li _1.12 Ni _0.8 Mn _0.1 Co _0.05 Al _0.05 O ₂ , Li _1.12 Ni _0.8 Mn _0.1 Co _{0.05 Mg 0.05} O ₂ , Li _1.12 Ni _0.8 Mn _0.1 Co _0.05 Ti _0.05 O ₂ , Li _1.12 Ni _0.8 Mn _0.1 Co _0.05 Ce _2. Li _1.12 Ni _0.8 Mn _0.1 Co _0.05 Yb _0.05 O ₂ , Li _1.2 Ni _0.6 Mn _0.35 Co _0.05 O ₂ , Li _1.25 Ni _0.6 Mn _0.3 Co _0.05 Al _0.05 O ₂ , Li _1.25 Ni _0.6 Mn _0.3 Co _0.05 O _Mg 2 _2. Li _1.25 Ni _0.6 Mn _0.3 Co _0.05 Ce _0.05 O ₂ , Li _1.3 Ni _0.6 Mn _0.3 Co _0.05 Al _0.05 O ₂ .

The positive electrode material provided by the present invention solves the one-stop problem that the lithium ion battery with silicon-based material as the negative electrode needs additional lithium supplementation and needs to be matched with a high-capacity positive electrode material.

A second aspect of the present invention provides a method for preparing the positive electrode material for the silicon-based battery, comprising the following steps:

S1, the nickel salt, manganese salt and M salt are mixed to prepare the first solution, in the inert gas, the first solution and the alkaline solution are respectively added to the reactor for stirring reaction, and the pH of the control solution is 7～13; Continue to stir and age for 18-26 h, vacuum filter, wash, and dry to obtain the precursor;

S2. Mix the precursor obtained in step S1 with the lithium salt and put it into a reaction furnace, react at 450-900° C. for 8-24 hours, cool and grind to obtain a positive electrode material for a silicon-based battery.

The second aspect of the present invention provides another preparation method of the positive electrode material for the silicon-based battery, comprising the following steps:

S1, the nickel salt and the manganese salt are mixed to prepare the first solution, in the inert gas, the first solution and the alkaline solution are respectively added to the reactor for stirring reaction, and the pH of the control solution is 7～13; Continue to stir after feeding 18 ~ 26h, vacuum filtration, washing, drying to obtain the precursor;

S2. Mix the precursor obtained in step S1 with M salt and lithium salt, put it into a reaction furnace, react at 450-900° C. for 8-24 hours, cool and grind to obtain a positive electrode material for silicon-based batteries.

In the preparation method provided by the present invention, a hydroxide-type or carbonate-type nickel-manganese precursor is prepared first, and then mixed with lithium salt (or lithium salt and M salt), and reacted to obtain lithium-rich nickel for silicon-based batteries Manganese cathode material. Compared with the conventional method for preparing positive electrode materials by mixing, on the one hand, the method of the present invention can obtain a lithium-rich nickel-manganese positive electrode material, which can effectively ensure the overall mass specific capacity of the positive electrode material, so that it can carry a part of irreversible lithium for use in the first charging process. On the other hand, the method of the present invention has good compatibility with the preparation method of the existing positive electrode material, does not require additional production investment such as equipment and environmental control, and saves the production cost of the battery.

In some embodiments, the lithium salt is at least one of lithium oxide, lithium carbonate, lithium nitrate, lithium acetate and lithium hydroxide; the nickel salt is nickel nitric acid at least one of salt, nickel carbonate, nickel oxalate and nickel oxide; the manganese salt is at least one of manganese nitrate, manganese carbonate, manganese oxalate and manganese oxide; the M salt is at least one of M nitrate, M carbonate, M acetate, M hydroxide and M oxide.

In some embodiments, the nickel, manganese, and M in the nickel salt, manganese salt, and M salt are denoted as metal A, and the molar ratio of the metal A to the lithium in the lithium salt is 1:(1.05～1.5 ). The molar amount of the metal A refers to the molar amount after adding all the metals, that is, the molar amount of nickel, manganese, and M metals and the molar ratio of lithium are 1: (1.05-1.5). Specifically, the molar ratio of the two can be 1:1.05, 1:1.1, 1:1.12, 1:1.15, 1:1.18, 1:1.2, 1:1.22, 1:1.25, 1:1.3, 1:1.4 or 1:1.5. The positive electrode material of the present invention is a lithium-rich positive electrode material, which can ensure that a part of irreversible lithium in the obtained positive electrode material itself is used to generate the SEI film during the first charging process, and at the same time, there is still a large amount of effective mass specific capacity for and High-capacity silicon-based anode materials are matched.

In some embodiments, in step S1, the preparation method of the precursor is as follows: a first solution is prepared by mixing nickel salt, manganese salt and M salt, and in an inert gas at 30-80° C., the first solution is mixed with The alkaline solution was added to the reactor with deionized water at a rate of 0.8-1.2 mL/min, and the stirring speed was 400-600 rpm/min, and the pH of the solution was controlled to be 7-13; the stirring was continued after feeding. The mixture was heated for 18 to 26 hours, vacuum filtered, washed, and dried at 100 to 120°C for 40 to 60 hours to obtain the precursor.

In some embodiments, in step S2, the lithium salt is first divided into a first part and a second part, the first part of the lithium salt is mixed with the precursor, reacted at 450-900° C. for 8-24 hours, cooled, and ground ; Add the second part of lithium salt and mix together, react at 450-900° C. for 8-24 hours, cool and grind to obtain a positive electrode material for a silicon-based battery.

In some embodiments, the mass ratio of the first part of the lithium salt to the second part of the lithium salt is (5-9): (5-1). By the method of adding lithium salt in distribution, the ratio of the surplus lithium amount (for silicon carbon negative electrode to form SEI film) and effective mass specific capacity (mass specific capacity that can be recovered after the first discharge) of the positive electrode material can be adjusted to Better matching the application of silicon-based lithium-ion batteries. Specifically, the mass ratio of the first part of the lithium salt to the second part of the lithium salt may be 5:5, 6:4, 7:3, 8:2 or 9:1. Preferably, the mass ratio of the first part of the lithium salt to the second part of the lithium salt is 5:5, 6:4, 7:3 or 8:2.

In some embodiments, in step S2, the first part of the lithium salt is mixed with the precursor, and the temperature is first heated to 450-650°C at a rate of 4-7°C/min, maintained for 1-3 hours, and then heated to 4-7°C at a rate of 4-7°C/min. The temperature was raised to 700-900°C at a rate of 4-7°C/min, kept for 10-24 hours, then cooled and ground; then the second part of the lithium salt was added and mixed together, and the temperature was raised to 450-650°C at a rate of 4-7°C/min, kept for 1 ~3h, then the temperature is raised to 700~900°C at a rate of 4~7°C/min, maintained for 10~24 hours, cooled, and ground to obtain a positive electrode material for a silicon-based battery.

2. Positive electrode

A third aspect of the present invention provides a positive electrode sheet, comprising a positive electrode current collector and a positive electrode active material layer coated on at least one surface of the positive electrode current collector, the positive electrode active material layer comprising the above-mentioned positive electrode for a silicon-based battery Material.

3. Lithium-ion battery

A fourth aspect of the present invention provides a lithium ion battery, comprising a positive electrode sheet, a negative electrode sheet, and a separator spaced between the positive electrode sheet and the negative electrode sheet, wherein the negative electrode active material in the negative electrode sheet is a silicon-based material, The positive electrode sheet is the positive electrode sheet described above.

Wherein, the silicon-based material may be selected from one or more of silicon-oxygen compounds, silicon-carbon composites, and silicon alloys.

In order to make the technical solutions and advantages of the present invention clearer, the present invention and its beneficial effects will be described in further detail below with reference to the specific embodiments and the accompanying drawings, but the embodiments of the present invention are not limited thereto.

Example 1

A positive electrode material for a silicon-based battery, the chemical formula of which is Li _1.05 Ni _0.8 Mn _0.1 Co _0.05 Al _0.05 O ₂ .

The preparation method of the positive electrode material for the silicon-based battery is as follows:

S1. Prepare an aqueous solution of NiSO ₄ , MnSO ₄ , CoSO ₄ , (Al) ₂ (SO ₄ ) ₃ (Ni ²⁺ , Mn ^{2 +} , Co ²⁺ , Al ³⁺ ) in a molar ratio of 8:1:0.5:0.5 The total concentration is 2mol L ^-1 ) 500mL, which is recorded as the first solution; 500mL of NaOH solution of 4mol L ^-1 is prepared as an alkaline solution; in an inert gas at 30 ~ 80 ℃, pass the first solution and the alkaline solution through The peristaltic pump was added to a five-necked flask reactor with 100 mL of deionized water at a speed of about 1 mL/min, and the reaction was stirred, and the stirring speed was 500 rpm/min. During the reaction, the pH of the solution was controlled by dripping ammonia water=10～13; Continue to stir and age for 24h after feeding; after the ageing is completed, the obtained precipitate is vacuum filtered, washed with deionized water for several times, and dried in a vacuum drying oven at 110 ° C for 48h to obtain the precursor (Ni _0.8 Mn _0.1 Co _0.05 Al _0.05 )(OH) ₂ .

S2. The precursor (Ni _0.8 Mn _0.1 Co _0.05 Al _0.05 ) (OH) ₂ and LiOH·H ₂ O (molar of metal A and Li=1:1.05) are mechanically mixed, and the mixture is put into a saggar and placed in a muffle In the furnace, with oxygen as the sintering atmosphere, the temperature was first heated to 450°C at a rate of 6°C/min, and kept for 2 hours; then the temperature was raised to 760°C at a rate of 6°C/min, and the temperature was kept for 12 hours; the furnace was cooled to room temperature and then ground to obtain Positive electrode material for silicon-based battery Li _1.05 Ni _0.8 Mn _0.1 Co _0.05 Al _0.05 O ₂ .

Example 2

A positive electrode material for a silicon-based battery, the chemical formula of which is Li _1.05 Ni _0.6 Mn _0.35 Co _0.05 O ₂ .

The preparation method of the positive electrode material for the silicon-based battery is as follows:

S1. Prepare 500 mL of an aqueous solution of NiSO ₄ , MnSO ₄ , and CoSO ₄ at 6:3.5:0.5 (the total concentration of Ni ²⁺ , Mn ²⁺ , Co ²⁺ is 2 mol L ^-1 ), and record it as the first solution; prepare 4 mol L 500 mL of NaOH solution of ^-1 was used as an alkaline solution; in an inert gas at 30-80 °C, the first solution and the alkaline solution were added to a five-part solution with 100 mL of deionized water at a speed of about 1 mL/min through a peristaltic pump. The reaction was stirred in the flask reactor, and the stirring speed was 500 rpm/min. During the reaction, the pH of the solution was controlled by dropwise addition of ammonia water = 10 to 13; after feeding, the stirring and aging were continued for 24 hours; after the aging was completed, the obtained precipitate was vacuum filtered. , washed with deionized water for several times, and dried in a vacuum drying oven at 110° C. for 48 h to obtain the precursor (Ni _0.6 Mn _0.35 Co _0.05 )(OH) ₂ .

S2. The precursor (Ni _0.6 Mn _0.35 Co _0.05 ) (OH) ₂ and Li ₂ CO ₃ (molar of metal A and Li=1:1.05) are mechanically mixed, and the mixture is put into a sagger and placed in a muffle furnace, With oxygen as the sintering atmosphere, the temperature was first heated to 650°C at a rate of 6°C/min, and kept for 2 hours; then the temperature was raised to 840°C at a rate of 6°C/min, and the temperature was kept for 12 hours. After cooling to room temperature with the furnace, the silicon battery was obtained by grinding. The positive electrode material Li _1.05 Ni _0.6 Mn _0.35 Co _0.05 O ₂ is used.

Example 3

The difference from Embodiment 1 is step S2.

S2. Weigh the precursor (Ni _0.8 Mn _0.1 Co _0.05 Al _0.05 ) (OH) ₂ and LiOH·H ₂ O (molar of metal A and Li=1:1.12), and divide LiOH·H ₂ O into 7 according to the mass ratio : 3 in two parts; firstly, the precursor was mechanically mixed with 70% LiOH·H ₂ O, the mixture was put into a sagger and placed in a muffle furnace, and oxygen was used as the sintering atmosphere. The temperature was increased to 450°C at a rate of 450°C and kept for 2h; then the temperature was raised to 760°C at a rate of 6°C/min, and the temperature was kept for 12h; cooled to room temperature with the furnace, and then ground; and then mixed with 30% LiOH·H ₂ O. The temperature was raised to 450°C at a rate of 6°C/min and kept for 2 hours; then the temperature was raised to 700°C at a rate of 6°C/min, and the temperature was kept for 12 hours; after cooling to room temperature with the furnace, grinding; the cathode material Li _1.12 Ni _0.8 for silicon-based batteries was obtained Mn _0.1 Co _0.05 Al _0.05 O ₂ .

The rest are the same as in Embodiment 1, and are not repeated here.

Example 4

The difference from Example 3 is that in step S2, the proportion of lithium salts added sequentially, the first time adding lithium salt accounting for 80%, and the second adding lithium salt accounting for 20%.

The rest are the same as in Embodiment 3, and are not repeated here.

Example 5

The difference from Example 3 is that in step S2, the proportion of lithium salts added sequentially, the first time adding a lithium salt accounting for 50%, and the second adding a lithium salt accounting for 50%.

The rest are the same as in Embodiment 3, and are not repeated here.

Example 6

The difference from Embodiment 2 is step S2.

S2. Weigh the precursor (Ni _0.6 Mn _0.35 Co _0.05 ) (OH) ₂ and Li ₂ CO ₃ (molar of metal A and Li=1:1.2), and divide Li ₂ CO ₃ into two parts of 8:2 according to the mass ratio ; First, the precursor is mechanically mixed with Li ₂ CO ₃ with a proportion of 80%, the mixture is put into a saggar and placed in a muffle furnace, and oxygen is used as the sintering atmosphere, and the temperature is first heated to 650 ° C at a rate of 6 ° C/min. , hold for 2h; then heat up to 840°C at a rate of 6°C/min, hold for 12h; cool down to room temperature with the furnace and grind; then add 20% Li ₂ CO ₃ and mix together, at a temperature of 6° C/min The temperature was increased to 450 °C at a rate of 2 h, and the temperature was maintained for 2 h; then the temperature was increased to 820 °C at a rate of 6 °C/min, and the temperature was maintained for 12 h; cooled to room temperature with the furnace and then ground; the cathode material for silicon-based batteries was obtained Li _1.12 Ni _0.8 Mn _0.1 Co _0.05 Al _0.05 O ₂ .

The rest are the same as those in Embodiment 2, and are not repeated here.

Example 7

The difference from Example 6 is that in step S2, the proportion of lithium salts added sequentially, the first time adding lithium salt accounting for 90%, and the second adding lithium salt accounting for 10%.

The rest are the same as in Embodiment 6, and are not repeated here.

Example 8

The difference from Example 6 is that in step S2, the proportion of lithium salts added sequentially, the first time adding a lithium salt accounting for 50%, and the second adding a lithium salt accounting for 50%.

The rest are the same as in Embodiment 6, and are not repeated here.

Example 9

A positive electrode material for a silicon-based battery, the chemical formula of which is Li _1.25 Ni _0.6 Mn _0.3 Co _0.05 Al _0.05 O ₂ .

The preparation method of the positive electrode material for the silicon-based battery is as follows:

S1. Prepare 500 mL of an aqueous solution of NiSO ₄ , MnSO ₄ , and CoSO ₄ at 6:3:0.5 (the total concentration of Ni ²⁺ , Mn ²⁺ , and Co ²⁺ is 2 mol L ^-1 ), which is recorded as the first solution; prepare 4 mol L 500 mL of NaOH solution of ^-1 was used as an alkaline solution; at 30-80 ℃ in an inert gas, the first solution and the alkaline solution were added to a fifth solution with 100 mL of deionized water at a speed of about 1 mL/min through a peristaltic pump. The reaction was stirred in the flask reactor, and the stirring speed was 500 rpm/min. During the reaction, the pH of the solution was controlled by dropwise addition of ammonia water = 10 to 13; after feeding, the stirring and aging were continued for 24 hours; after the aging was completed, the obtained precipitate was vacuum filtered. , washed with deionized water for several times, and dried in a vacuum drying oven at 110° C. for 48 h to obtain the precursor (Ni _0.6 Mn _0.3 Co _0.05 )(OH) ₂ .

S2. Weigh the precursor (Ni _0.6 Mn _0.3 Co _0.05 ) (OH) ₂ and Li ₂ CO ₃ (molar of metal A and Li=1:1.25), and divide Li ₂ CO ₃ into two parts of 8:2 according to the mass ratio ; First, the precursor is mechanically mixed with Li ₂ CO ₃ with a proportion of 80%, the mixture is put into a saggar and placed in a muffle furnace, and oxygen is used as the sintering atmosphere, and the temperature is first heated to 650 ° C at a rate of 6 ° C/min. , hold for 2h; then heat up to 840°C at a rate of 6°C/min, hold for 12h; cool down to room temperature with the furnace and grind; then add Al(OH) ₃ and 20% Li ₂ CO ₃ to mix together, The temperature was raised to 450°C at a rate of 6°C/min, and kept for 2 hours; then the temperature was raised to 820°C at a rate of 6°C/min, and the temperature was kept for 12 hours; cooled to room temperature with the furnace, and then ground; the cathode material for silicon-based batteries Li _1.25 Ni _0.6 Mn _0.3 Co _0.05 Al _0.05 O ₂ .

The XRD test of the positive electrode materials for silicon-based batteries obtained in the above examples 1 to 3, 6 and 9 is shown in Figures 1 to 5. It can be seen from the figures that the present invention has successfully prepared a positive electrode for silicon-based batteries. Material Li _1+a Ni _b Mn _c M _cd O ₂ .

The positive electrode materials for silicon-based batteries obtained in the above Examples 1 to 9 were applied to the positive electrode sheet, and the positive electrode sheet was prepared by mixing and sizing according to the active material (ie, the positive electrode material for silicon-based batteries), super P, and PVDF binder.

The obtained positive electrode sheet was applied to the button battery to test the performance, the counter electrode used was a metal lithium sheet, the electrolyte was EC, DMC, and EMC (volume ratio 1:1:1) solution of 1mol/L LiPF ₆ , and the separator was celgard 2400 polypropylene film. During the test, the highest cut-off voltage of Example 1 and Examples 3 to 5 was 4.2V, the highest cut-off voltage of Example 2 and Examples 6 to 9 was 4.4V, and the first charge and discharge currents were both 0.1C.

In addition, the obtained positive electrode sheet was prepared into a full battery and tested its performance. Silicon carbon was used as the negative electrode material, the electrolyte was 1 mol/L LiPF ₆ EC, DMC, and EMC (volume ratio 1:1:1) solution, and the diaphragm was celgard2400 Polypropylene film, made into soft pack full battery (404050). During the test, the maximum cut-off voltage of Example 1 and Examples 3 to 5 was 4.2V, and the maximum cut-off voltage of Example 2 and Examples 6 to 9 was 4.4V. The first charge and discharge currents were both 0.1C, and the cycle charge and discharge The current is 1C.

The test results are shown in Table 1 below.

Table 1

It can be seen from the above test results that the positive electrode material Li _{1+ a} Ni _b Mn _c M _cd O ₂ obtained by the preparation method of the present invention contains a part of irreversible lithium which can be used to generate SEI during the first charging process. At the same time, the effective mass specific capacity is also high, which can well match the silicon-based negative electrode material. Therefore, the lithium-ion battery composed of the positive electrode material and the silicon-based negative electrode material of the present invention does not require additional lithium supplementation, the preparation process is simple, and the production cost is low. It solves the problems of high technical difficulty and high production cost of pre-lithiation in the current silicon-based lithium-ion battery.

In addition, from the comparison of Examples 1, 3-5 and 2, 6-8, it can also be seen that when the preparation method of adding lithium salt by distribution is adopted, the surplus lithium amount of the positive electrode material (for silicon carbon negative electrode) can be obtained. The ratio of the effective mass specific capacity (the mass specific capacity that can be recovered after the first discharge) can be adjusted, which can improve the irreversible capacity of the cathode material and make it more used in the formation of the SEI film to ensure the subsequent cycle performance. Preferably, when the added mass ratio of the two parts of the lithium salt is 5:5 to 8:2, the irreversible capacity is effectively increased, and a relatively excellent capacity retention rate can still be maintained after 500 cycles of cycling.

Based on the disclosure and teaching of the above specification, those skilled in the art to which the present invention pertains can also make changes and modifications to the above-described embodiments. Therefore, the present invention is not limited to the above-mentioned specific embodiments, and any obvious improvement, replacement or modification made by those skilled in the art on the basis of the present invention falls within the protection scope of the present invention. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims (10)

1. A positive electrode material for a silicon battery, characterized in that it has a chemical formula of Li_1+aNi_bMn_cM_c-dO₂Wherein a is more than or equal to 0 and less than or equal to 1, b is more than 0 and less than 1, c is more than 0 and less than 1, d is more than or equal to c, and b +2c-d is less than 1+ a; m is at least one of Ti, Zr, La, Ce, Pr, Nd, Nb, Sm, Al, Mg, Sr, Ba, Co, Zn, Sn, Bi, Sb, Si, Tb, Bi, Yb, Lu, B and Y.

2. A method for producing the positive electrode material for a silicon-based battery according to claim 1, comprising the steps of:

s1, mixing nickel salt and manganese salt to prepare a first solution, adding the first solution and an alkaline solution into a reactor respectively in an inert gas, stirring and reacting, and controlling the pH value of the solution to be 7-13; continuously stirring and aging for 18-26 h after feeding, carrying out vacuum filtration, washing and drying to obtain a precursor;

s2, mixing the precursor obtained in the step S1 with lithium salt, loading the mixture into a reaction furnace, reacting for 8-24 hours at 450-900 ℃, cooling and grinding to obtain the positive electrode material for the silicon battery;

wherein, the M salt is mixed with the nickel salt and the manganese salt to prepare a first solution in step S1, or is mixed with the precursor and the lithium salt obtained in step S1 to react in step S2.

3. The method for producing a positive electrode material for a silicon-based battery according to claim 2, wherein the lithium salt is at least one of lithium oxide, lithium carbonate, lithium nitrate, lithium acetate, and lithium hydroxide; the nickel salt is at least one of nitrate of nickel, carbonate of nickel, nickel oxalate, nickel acetate and nickel oxide; the manganese salt is at least one of nitrate of manganese, carbonate of manganese, manganese oxalate, manganese acetate and manganese oxide; the M salt is at least one of nitrate of M, carbonate of M, acetate of M, hydroxide of M and oxide of M.

4. The method of claim 2, wherein nickel, manganese, and M in the nickel salt, manganese salt, and M salt are represented as a metal a, and a molar ratio of the metal a to lithium in the lithium salt is 1: (1.05-1.5).

5. The method of manufacturing a positive electrode material for a silicon-based battery according to claim 2, wherein the precursor is manufactured in step S1 by: mixing nickel salt, manganese salt and M salt to prepare a first solution, adding the first solution and an alkaline solution into a reactor with deionized water at the speed of 0.8-1.2 mL/min respectively at the temperature of 30-80 ℃ in inert gas, stirring for reaction at the speed of 400-600 rpm/min, and controlling the pH value of the solution to be 7-13; and after feeding, continuously stirring and aging for 18-26 h, carrying out vacuum filtration, washing, and drying at 100-120 ℃ for 40-60 h to obtain a precursor.

6. The method of claim 2 or 5, wherein in step S2, the lithium salt is divided into a first part and a second part, the first part of lithium salt is mixed with the precursor, and the mixture is reacted at 450-900 ℃ for 8-24 h, cooled and ground; and then adding a second part of lithium salt, mixing, reacting for 8-24 h at 450-900 ℃, cooling, and grinding to obtain the positive electrode material for the silicon battery.

7. The method for producing the positive electrode material for a silicon-based battery according to claim 6, wherein the mass ratio of the first lithium salt to the second lithium salt is (5-9): (5-1).

8. The method for preparing the positive electrode material for the silicon-based battery according to claim 7, wherein in step S2, the first part of lithium salt is mixed with the precursor, the temperature is raised to 450-650 ℃ at a rate of 4-7 ℃/min, the temperature is maintained for 1-3 h, the temperature is raised to 700-900 ℃ at a rate of 4-7 ℃/min, the temperature is maintained for 10-24 h, and then the mixture is cooled and ground; and then adding a second part of lithium salt, mixing, heating to 450-650 ℃ at the speed of 4-7 ℃/min, preserving heat for 1-3 h, heating to 700-900 ℃ at the speed of 4-7 ℃/min, preserving heat for 10-24 h, cooling, and grinding to obtain the positive electrode material for the silicon battery.

9. A positive electrode sheet comprising a positive electrode current collector and a positive electrode active material layer coated on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer comprises the positive electrode material for a silicon-based battery according to claim 1.

10. A lithium ion battery comprising a positive plate, a negative plate and a separator interposed between the positive plate and the negative plate, wherein the negative active material in the negative plate is a silicon-based material, and the positive plate is the positive plate according to claim 9.

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