Phosphorus-carbon composite negative electrode material, and preparation method and application thereof

Abstract

The application relates to a phosphorus-carbon composite negative electrode material, which is a composite capsule structure and comprises porous carbon, ternary phosphide A x L 1‑x M y P and a carbon coating layer; in the ternary phosphide A x L 1‑x M y P, A is any one of Fe, Co and Ni, L is Ge or Sn, M is Se or Te, 0.1<=x<=0.5 and 0.5<=y<=1.5. Compared with single metal phosphide and binary metal phosphide, the ternary phosphide A x L 1‑x M y P of the application can significantly improve the conductivity, specific capacity and cycle stability of the material. The phosphorus-carbon composite negative electrode material prepared by the method of the application exhibits good electrochemical performance when used in a secondary ion battery, the first coulombic efficiency of lithium ions and sodium ions is more than 80%, the charging specific capacity is more than 1500 mAh / g, and the cycle capacity retention rate after 200 cycles is more than 85%.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of secondary ion battery negative electrode materials, and particularly relates to a phosphorus-carbon composite negative electrode material and a preparation method and application thereof. BACKGROUND

[0002] Under the national double carbon strategy goal, in order to meet the growing demand for energy storage batteries in the fields of consumer electronics, electric tools, mobile devices and the like, secondary ion batteries with high energy density and safety are one of the important directions for the development of next-generation efficient energy storage devices. However, the electrode materials used in traditional secondary ion batteries are limited in type, low in capacity, and difficult to meet the current demand for energy storage batteries. Therefore, the development of next-generation high-energy-density negative electrode materials has become a hot spot of current research and an important development direction for future large-scale energy storage battery technology.

[0003] Since phosphorus and lithium, sodium and potassium can form Li3P, Na3P and K3P alloys with a theoretical capacity as high as 2596 mAh g -1 , which almost exceeds the capacity of the currently commercialized secondary ion battery negative electrode materials, phosphorus is considered to be one of the most promising negative electrode materials. Moreover, red phosphorus (RP) has the advantages of abundant reserves, easy availability in commerce, chemical stability, easy control and the like. However, the electrical conductivity of red phosphorus is extremely low (about 10 -12 S m -1 ) and is accompanied by a large volume expansion (>300%) during the charging and discharging process, which leads to a low cycle life of red phosphorus as a secondary battery negative electrode. Despite some shortcomings, considering safety and practicality, red phosphorus as a secondary battery negative electrode material is still intensively studied. At present, the most widely studied phosphorus-based materials include metal phosphides and phosphorus-carbon composite materials.

[0004] Phosphorus can form metal phosphides with other transition metals, improve the electrical conductivity of the material and effectively buffer the volume effect during the charging and discharging process, thereby improving the electrochemical performance and stability of the material. Professor Kim's research group first reported Sn4P3 as a negative electrode material for sodium ion batteries, and the prepared Sn4P3 alloy negative electrode material has a reversible capacity of 718 mAh g -1and high capacity retention rate (Advanced Materials 2014, 26(24): 4139-4144). Professor Liu's group adopted the method of chemical deposition to deposit metal Ni2P on the surface of red phosphorus particles, and prepared RP@Ni-P material with core-shell structure by adjusting the deposition thickness. The in-situ formed Ni2P has strong contact with red phosphorus and high conductivity, which ensures the integrity of the electrode structure and relieves the volume expansion of red phosphorus (Energy & Environmental Science 2015, 8(12): 3531-3538). The above results show that the alloying with conductive metal elements can effectively improve the conductivity of phosphorus, relieve the volume expansion, and improve the electrochemical activity of the material as the negative electrode material of sodium ion battery. However, due to the alloying, the loading capacity of phosphorus is reduced, so that the capacity of metal phosphide is relatively low. In contrast, carbon materials have outstanding conductivity and diverse structures, making them the first choice for phosphorus-carbon negative electrode materials. On the one hand, the composite of phosphorus and carbon material, and the carbon material as a carrier support, effectively prevent the agglomeration of phosphorus particles and improve the loading capacity of phosphorus. Secondly, the excellent conductivity of carbon material can improve the conductivity of the composite material.

[0005] Professor Sun's group found that the P-C bond remained stable during the cycle process, ensuring that phosphorus and carbon maintained good contact, so that the composite material had high initial discharge capacity, but the cycle performance of the phosphorus-carbon material was always limited due to the exposure of phosphorus (Nano Letters 2014, 14(8), 4573-4580).

[0006] Therefore, it is urgent to develop a high-capacity, high-first-coulomb-efficiency and high-cycle-performance phosphorus-carbon negative electrode material, which is the key to realizing commercial application and provides technical support for developing high-specific-energy secondary ion batteries. SUMMARY

[0007] The application provides a phosphorus-carbon composite negative electrode material and a preparation method thereof, which is applied to lithium ion batteries and sodium ion batteries and has high coulomb efficiency, reversible capacity and excellent cycle stability.

[0008] To achieve the above object, the application adopts the following technical solutions.

[0009] A phosphorus-carbon composite negative electrode material has a composite capsule structure, which comprises porous carbon, ternary phosphide A x L 1-x M y P loaded in the pore channel of the porous carbon and a carbon coating layer; the ternary phosphide A x L 1-x M yIn P, A is any one of Fe, Co and Ni, L is Ge or Sn, M is Se or Te, 0.1≤x≤0.5, 0.5≤y≤1.5.

[0010] A is a Group VIII transition metal element, L is a Group IVA post-transition metal, and M is a non-metal element. The inventors unexpectedly found that the ternary phosphide formed by matching the three elements can significantly improve the electrical conductivity and specific capacity of the material compared to single-metal phosphide and binary metal phosphide. In addition, in the process of electrochemical sodium, Ge and Sn in L can alloy with Na to form corresponding alloys NaGe, Na 15 Sn4; Se and Te in M can react with Na to form corresponding compounds Na2Se, Na2Te; these alloys and compounds can produce a synergistic effect with Na3P generated in the process of electrochemical sodium, effectively improving the reaction kinetics of Na + ; at the same time, Na3P can also act as a buffer to prevent Ge and Se nanocrystals from aggregating during the alloying process, thereby reducing the volume expansion; the improvement of the reaction kinetics of Na + and the effective inhibition of volume expansion during the alloying process make the battery have good cycle stability. Similarly, in lithium batteries, corresponding alloys and compounds can also be formed, thereby improving the electrochemical performance of the battery.

[0011] Further, the ternary phosphide A x L 1-x M y In P, A is Ni, L is Sn, and M is Se.

[0012] Further, the ternary phosphide A x L 1-x M y P, 0.2≤x≤0.4, 0.8≤y≤1.2.

[0013] Further, the pore size distribution of the porous carbon is as follows: the volume fraction of micropores (pore size < 2 nm) is 60-90%, preferably 70-80%; the volume fraction of mesopores (pore size 2-50 nm) is 10-40%, preferably 20-30%.

[0014] Further, the porous carbon has a pore volume of 0.6-1.5 m 3 / g, a specific surface area of 800-2100 m 2 / g, and a particle size D50 of 2-10 μm.

[0015] Further, in the phosphorus-carbon composite negative electrode material, the content of the porous carbon is 30wt%-50wt%, the ternary phosphide A x L 1-x M yP accounts for 50wt%-70wt%, and the rest is a carbon coating layer.

[0016] In a second aspect, the present application provides a preparation method of the phosphorus-carbon composite negative electrode material, comprising the following steps:

[0017] (S1) according to the stoichiometric ratio of A x L 1-x M y P, dissolving A salt and L salt in a solvent to form a mixed solution; according to the stoichiometric ratio of A in A salt and porous carbon, (5-10) g of porous carbon is added, and A ion and L ion loaded porous carbon is obtained by immersion adsorption and centrifugal drying;

[0018] (S2) heat treating the A ion and L ion loaded porous carbon in a reducing atmosphere to reduce A ion and L ion, and obtaining A

[0019] (S3) according to the stoichiometric ratio of A x L 1-x M y P, mixing M source with A and L loaded porous carbon to obtain a mixture; heat treating the mixture with a phosphorus source at 500-600℃ for 2-6h; and then controlling the temperature to obtain A x L 1-x M y P loaded porous carbon;

[0020] (S4) coating the A x L 1-x M y P loaded porous carbon by gas deposition method to obtain the phosphorus-carbon composite negative electrode material.

[0021] Further, in step (S1), the A salt is nitrate and / or chloride salt of A, and the L salt is nitrate and / or chloride salt of L; the solvent is at least one of ethanol, isopropanol and water.

[0022] Further, in step (S1), the amount ratio of porous carbon to mixed solution is 1g:(10-20)mL; the immersion adsorption is 24-48h.

[0023] Further, in step (S2), the reducing atmosphere includes hydrogen, preferably, the volume fraction of hydrogen is 5-20%; preferably, the reducing atmosphere is hydrogen-argon mixed atmosphere; the heat treatment conditions are 300-600℃ for 3-6h.

[0024] Further, in step (S3), the ratio of the total moles of A elements in the A salt, L elements in the L salt, M elements in the M source, to the moles of P elements in the P source is 1:(5-10), i.e., the molar ratio of (A+L+M):P is 1:(5-10); the P source is red phosphorus or a phosphide; the phosphide is at least one of ammonium dihydrogen phosphate, sodium dihydrogen phosphate, and triphenylphosphine.

[0025] Further, in step (S3), when the P source is red phosphorus: the heat treatment is vacuum heat treatment; the temperature control treatment is four-stage temperature control treatment: the first stage is cooling to 440-460℃, holding for 1-10h; the second stage is cooling to 410-430℃, holding for 1-10h; the third stage is cooling to 400-410℃, holding for 1-10h, and then cooling to room temperature; the fourth stage is heating from room temperature to 280-400℃, holding for 10-40h, and then cooling to room temperature; the cooling rate of the first, second, and third stages is 0.1-1℃ / min, and the heating rate of the fourth stage is 1-10℃ / min.

[0026] When the P source is a phosphide: the heat treatment is heat treatment under an inert atmosphere; the inert atmosphere is nitrogen and / or argon; the temperature control treatment is natural cooling to room temperature.

[0027] In step (S3), when the P source is red phosphorus, the first stage of cooling to 440-460℃ for 1-10h and the second stage of cooling to 410-430℃ for 1-10h are to allow the excess red phosphorus to slowly and uniformly deposit on the porous carbon substrate when the temperature is reduced to near the sublimation point; the third stage of cooling to 400-410℃ for 1-10h and then cooling to room temperature is to allow the red phosphorus to completely condense and deposit; after the three-stage cooling treatment, the excess red phosphorus is converted into white phosphorus and deposited on the porous carbon substrate. The fourth stage of heating from room temperature to 280-400℃ for 10-40h is to allow the deposited white phosphorus to sublimate again to red phosphorus, avoiding the presence of toxic white phosphorus.

[0028] In step (S4), the process for forming the carbon coating layer is well known to those skilled in the art, such as gas phase deposition using a carbon source gas selected from at least one of C1-4alkanes, C2-4alkenes, and C2-4alkynes.

[0029] In a third aspect, the application also provides the use of the above-mentioned phosphorus-carbon composite negative electrode material in lithium ion batteries and sodium ion batteries.

[0030] Compared with the prior art, the application has the following advantages:

[0031] 1) Compared with single metal phosphide and binary metal phosphide, the ternary phosphide A x L 1-x My P can significantly improve the conductivity and specific capacity of the material. In addition, in the process of electrochemical sodium, lithium or potassium, Ge and Sn in L can be alloyed with Na, Li or K to form the corresponding alloy; Se and Te in M can react with Na, Li to form the corresponding compound; these alloys and compounds can produce a synergistic effect with Na3P generated in the process of electrochemical sodium or Li3P generated in the process of electrochemical lithium, which can effectively improve the reaction kinetics of corresponding Na + or Li + ; at the same time, Na3P and Li3P can also act as buffers to prevent Ge and Se nanocrystals from aggregating during alloying, thereby reducing the volume expansion; the improvement of the reaction kinetics of the corresponding ions and the effective inhibition of the volume expansion during alloying make the battery have good cycle stability.

[0032] 2) Since the ternary phosphide A x L 1-x M y P fills in the pores of the porous carbon, its outward expansion is constrained by the carbon layer shell, and the existence of the porous core provides a buffer for its inward expansion, so that the phosphorus-carbon composite negative electrode material provided by the application can effectively inhibit the structural rupture caused by the volume change of phosphorus, avoid the large loss of active sites, and improve the cycle stability.

[0033] 3) The phosphorus-carbon composite negative electrode material prepared by the method of the application has good electrochemical performance when used in a secondary ion battery, the first coulombic efficiency of lithium ions and sodium ions is more than 80%, the charge specific capacity is more than 1500 mAh / g, and the cycle capacity retention rate is more than 85% after 200 cycles. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 It is the XRD pattern of the phosphorus-carbon composite negative electrode material prepared in Example 1 of the application.

[0035] Figure 2 It is the SEM pattern of the phosphorus-carbon composite negative electrode material prepared in Example 1 of the application.

[0036] Figure 3 It is the TEM pattern of the phosphorus-carbon composite negative electrode material prepared in Example 1 of the application.

[0037] Figure 4 It is the charge-discharge curve of the phosphorus-carbon composite negative electrode material prepared in Example 1 of the application as a negative electrode of a sodium ion battery. DETAILED DESCRIPTION

[0038] The application will be further described below in conjunction with specific embodiments, but the application is not limited to the following embodiments.

[0039] The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0040] The particle size D50 of the porous carbon is 4.6 μm, and the specific surface area is about 1800 m 2 / g pore volume is about 1.2 cm 3 / g.

[0041] The hearth size of the CVD tube furnace is: diameter 6 cm, length 100 cm.

[0042] Example 1 (A x L 1-x M y In P, A is Fe, L is Ge, M is Se, x = 0.1, y = 0.5

[0043] The specific steps are as follows:

[0044] (S1) Take 0.1 mmol of iron chloride FeCl2 and 0.9 mmol of GeCl4, dissolve them in 5 ml of pure water to form a mixed solution; add 0.5 g of porous carbon to the mixed solution, ultrasonically stir and immerse for 24 h, centrifuge and dry to obtain Fe 2+ and Ge 4+ loaded porous carbon.

[0045] (S2) Place the Fe 2+ and Ge 4+ loaded porous carbon in a tube furnace, heat to 300℃ at a heating rate of 5℃ / min under a 10% hydrogen-argon atmosphere for 5 h, and cool to room temperature to obtain Fe, Ge loaded porous carbon material;

[0046] (S3) Mix the Fe, Ge loaded porous carbon with 0.5 mmol of selenium powder and 0.3 g of red phosphorus powder to obtain a mixture; place the mixture in a sealed polymerization tube with a vacuum degree of 0.01-10 Pa, and heat to 500℃ at a heating rate of 5℃ / min for 5 h; then perform four-stage temperature control treatment, first stage: cool to 440℃ at a rate of 0.1℃ / min, and keep for 2 h; second stage: cool to 425℃ at a rate of 0.1℃ / min, and keep for 2 h; third stage: cool to 416℃ at a rate of 0.1℃ / min, and keep for 2 h, then cool to room temperature; fourth stage: heat to 300℃ at a rate of 5℃ / min, and keep for 30 h, and naturally cool to room temperature to obtain Fe 0.1 Ge 0.9 Se 0.5 P loaded porous carbon;

[0047] (S4) Place the Fe 0.1 Ge 0.9 Se 0.5The porous carbon loaded with P is placed in a CVD furnace with a rotation speed of 20 rpm, and helium gas is introduced at a flow rate of 6 L / min, and the temperature is raised to 500 DEG C under the helium gas environment, then acetylene gas is introduced at a flow rate of 3 L / min to keep the temperature at 500 DEG C for 3 h of gas phase deposition, and the carbon particles formed by the decomposition of acetylene gas are deposited on the Fe 0.1 Ge 0.9 Se 0.5 The surface of the porous carbon loaded with P, i.e. the carbon coating layer, is finally obtained, and the phosphorus-carbon composite negative electrode material is obtained.

[0048] The XRD pattern of the phosphorus-carbon composite negative electrode material prepared in Example 1 is shown in Figure 1 The SEM pattern is shown in Figure 2 The TEM pattern is shown in Figure 3 .

[0049] Example 2 (A x L 1-x M y P, A is Co, L is Ge, M is Te, x = 0.1, y = 0.5)

[0050] The rest is the same as Example 1, the difference is that the types of A, L and M are different, A is Co, L is Ge, and M is Te, and the specific steps are as follows:

[0051] (S1) 0.1 mmol of cobalt nitrate (Co(NO3)2·6H2O) and 0.9 mmol of GeCl4 are dissolved in 5 ml of pure water to form a mixed solution; 0.5 g of porous carbon is added to the mixed solution, and ultrasonic stirring is used for immersion for 24 h, and then centrifugal drying is performed to obtain porous carbon loaded with Co 2+ and Ge 4+ .

[0052] (S2) The porous carbon loaded with Co 2+ and Ge 4+ is placed in a tube furnace, and heated to 400 DEG C at a heating rate of 5 DEG C / min under a 10% hydrogen-argon atmosphere for 4 h of thermal reduction, and then cooled to room temperature to obtain a porous carbon material loaded with Co and Ge;

[0053] (S3) The Co, Ge loaded porous carbon is mixed with 0.5 mmol tellurium powder and 0.3 g red phosphorus powder to obtain a mixture; the mixture is placed in a sealed polymerization tube with a vacuum degree of 0.01-10 Pa, and heated to 550 ℃ at a heating rate of 5 ℃ / min for 4 h; then four-stage temperature control treatment is carried out, the first stage: cooling to 440 ℃ at a rate of 0.1 ℃ / min, and keeping for 1 h; the second stage: cooling to 425 ℃ at a rate of 0.1 ℃ / min, and keeping for 4 h; the third stage: cooling to 416 ℃ at a rate of 0.1 ℃ / min, and keeping for 3 h and then cooling to room temperature; the fourth stage: heating to 300 ℃ at a rate of 5 ℃ / min, and keeping for 30 h, and then naturally cooling to room temperature, to obtain Co 0.1 Ge 0.9 Te 0.5 P loaded porous carbon.

[0054] (S4) The Co 0.1 Ge 0.9 Te 0.5 P loaded porous carbon is placed in a CVD furnace for carbon coating by gas deposition method, and the specific process is the same as that in Example 1, and finally a phosphorus-carbon composite negative electrode material is obtained.

[0055] Example 3(A x L 1-x M y P, A is Ni, L is Sn, M is Se, x=0.1, y=0.5)

[0056] The specific steps are as follows:

[0057] The rest is the same as Example 1, except that the types of A, L and M are different, A is Ni, L is Sn, M is Se, x=0.1, y=0.05, and the specific steps are as follows:

[0058] (S1) 0.1 mmol of Ni(NO3)2·6H2O and 0.9 mmol of SnCl2·2H2O are dissolved in 8 ml of pure water to form a mixed solution; 0.5 g of porous carbon is added to the mixed solution, and ultrasonic stirring is carried out for 24 h, and then centrifuged and dried to obtain Ni 2+ and Sn 2+ loaded porous carbon.

[0059] (S2) The porous carbon of the Ni 2+ and Sn 2+ loaded porous carbon is placed in a tube furnace, heated to 600 ℃ at a heating rate of 5 ℃ / min under a 10% hydrogen-argon atmosphere for 3 h, and then cooled to room temperature to obtain a Ni, Sn loaded porous carbon material;

[0060] (S3) The porous carbon loaded with Ni, Sn was mixed with 0.5 mmol selenium powder, 1.2 g sodium dihydrogen phosphate to obtain a mixture; the mixture was placed in a sealed polymerization tube with a vacuum degree of 0.01-10 Pa and heated to 550 ℃ at a heating rate of 5 ℃ / min for 4 h; and then naturally cooled to room temperature to obtain the porous carbon loaded with Ni 0.1 Sn 0.9 Se 0.5 P.

[0061] (S4) The porous carbon loaded with Ni 0.1 Sn 0.9 Se 0.5 P was placed in a CVD furnace for carbon coating by a gas deposition method, and the specific process was the same as that in Example 1, and finally a phosphorus-carbon composite negative electrode material was obtained.

[0062] Example 4 (A x L 1-x M y P, A is Ni, L is Sn, M is Te, x = 0.1, y = 0.5)

[0063] The rest is the same as Example 1, the difference lies in the types of A, L and M, A is Ni, L is Sn, M is Te, x = 0.1, y = 0.05, and the specific steps are as follows:

[0064] (S1) 0.1 mmol of Ni(NO3)2·6H2O and 0.9 mmol of SnCl2·2H2O were dissolved in 8 ml of pure water to form a mixed solution; 0.5 g of porous carbon was added to the mixed solution and ultrasonically stirred for 24 h, then centrifuged and dried to obtain the porous carbon loaded with Ni 2+ and Sn 2+ .

[0065] (S2) The porous carbon loaded with Ni 2+ and Sn 2+ was placed in a tube furnace and heated to 600 ℃ at a heating rate of 5 ℃ / min under a 10% hydrogen-argon atmosphere for 3 h, and then cooled to room temperature to obtain the porous carbon material loaded with Ni and Sn;

[0066] (S3) The porous carbon loaded with Ni, Sn was mixed with 0.5 mmol tellurium powder, 1.2 g ammonium dihydrogen phosphate to obtain a mixture; the mixture was placed in a sealed polymerization tube with a vacuum degree of 0.01-10 Pa and heated to 600 ℃ at a heating rate of 5 ℃ / min for 3 h; and then naturally cooled to room temperature to obtain the porous carbon loaded with Ni 0.1 Sn 0.9 Te 0.5 P.

[0067] (S4) The porous carbon loaded with Ni 0.1Sn 0.9 Te 0.5 P loaded porous carbon is placed in a CVD furnace for carbon coating by gas deposition method, and the specific process is the same as that in Example 1, and finally a phosphorus-carbon composite negative electrode material is obtained.

[0068] Example 5 (A x L 1-x M y P, A is Fe, L is Ge, M is Se, x = 0.2, y = 0.8)

[0069] The specific steps are as follows:

[0070] The rest is the same as Example 1, the difference is that the ratio of A, L and M is different, x = 0.2, y = 0.8, and accordingly, Fe 0.2 Ge 0.8 Se corresponding stoichiometric ratio of each chemical element is prepared in step (S1) and step (S3), and finally a phosphorus-carbon composite negative electrode material is obtained.

[0071] Example 6 (A x L 1-x M y P, A is Fe, L is Ge, M is Se, x = 0.2, y = 1.2)

[0072] The rest is the same as Example 1, the difference is that the ratio of A, L and M is different, x = 0.2, y = 1.2, and accordingly, Fe 0.2 Ge 0.8 Se 1.2 corresponding stoichiometric ratio of each chemical element is prepared in step (S1) and step (S3), and finally a phosphorus-carbon composite negative electrode material is obtained.

[0073] Example 7 (A x L 1-x M y P, A is Fe, L is Ge, M is Se, x = 0.3, y = 1.2)

[0074] The rest is the same as Example 1, the difference is that the ratio of A, L and M is different, x = 0.3, y = 1.2, and accordingly, Fe 0.3 Ge 0.7 Se 1.2 corresponding stoichiometric ratio of each chemical element is prepared in step (S1) and step (S3), and finally a phosphorus-carbon composite negative electrode material is obtained.

[0075] Example 8 (A x L 1-x M y P, A is Fe, L is Ge, M is Se, x = 0.4, y = 1.5)

[0076] The rest is the same as example 1, the difference is that the ratio of A, L, M is different, x = 0.4, y = 1.5, and accordingly, Fe 0.4 Ge 0.6 Se 1.5 The stoichiometric ratio of each corresponding chemical element is dosed in step (S1) and step (S3), and finally a phosphorus-carbon composite negative electrode material is obtained.

[0077] Example 9 (A x L 1-x M y P, A is Fe, L is Ge, M is Se, x = 0.5, y = 1.5)

[0078] The rest is the same as example 1, the difference is that the ratio of A, L, M is different, x = 0.5, y = 1.5, and accordingly, Fe 0.5 Ge 0.5 Se 1.5 The stoichiometric ratio of each corresponding chemical element is dosed in step (S1) and step (S3), and finally a phosphorus-carbon composite negative electrode material is obtained.

[0079] Comparative example 1

[0080] The rest is the same as example 1, the difference is that the type of A, L, M is different, A is Zn, L is Mn, M is V, and accordingly, Zn 0.1 Mn 0.9 V 0.5 The stoichiometric ratio of each corresponding chemical element is dosed in step (S1) and step (S3), and finally a phosphorus-carbon composite negative electrode material is obtained.

[0081] Comparative example 2

[0082] The rest is the same as example 1, the difference is that A, L is the same metal Fe, that is, binary metal phosphorus FeSe 0.5 P, and accordingly, FeSe 0.5 P The stoichiometric ratio of each corresponding chemical element is dosed in step (S1) and step (S3), and finally a phosphorus-carbon composite negative electrode material is obtained.

[0083] Test and analysis

[0084] The phosphorus-carbon composite negative electrode materials prepared in the above examples and comparative examples were tested for electrochemical performance according to the following method: the phosphorus-carbon composite negative electrode material, carbon black and carboxymethyl cellulose (CMC) were mixed with a mass ratio of 8:1:1 to form a slurry (the mass ratio of CMC and SBR was 2:3), the slurry was uniformly coated on a copper foil current collector, and after vacuum drying for 12 h, a working electrode was prepared; a sodium flake (lithium flake or potassium flake) was used as a counter electrode, a glass fiber membrane (purchased from the British Whatman Company) or a Celgard membrane was used as a separator, 1 mol / L NaPF6 (1 mol / L LiPF6 or 1 mol / L KPF6) (the solvent was a mixture of ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1) was used as an electrolyte, and the electrolyte was added with 1% VC and 5% FEC by volume fraction, and a button cell was assembled in an argon atmosphere in a German Braun inert gas glove box.

[0085] The charge-discharge curve of the phosphorus-carbon composite negative electrode material prepared in Example 1 as a sodium ion battery negative electrode is shown in FIG. 1. Figure 4

[0086] The above assembled battery was subjected to charge-discharge test on a LAND charge-discharge tester, and the data are shown in Table 1.

[0087] Table 1: Electrochemical performance test

[0088]

[0089]

[0090] In summary, as can be seen from the examples and comparative examples, the phosphorus-carbon composite negative electrode material prepared by the method of the present application has high first coulomb efficiency and capacity when used in a secondary ion battery, the first coulomb efficiency is more than 80% in lithium ion and sodium ion tests, the specific charge capacity is more than 1500 mAh / g, and the cycle capacity retention rate is more than 85% after 200 cycles.

[0091] The applicant declares that the above examples illustrate the detailed preparation method of the present application, but the present application is not limited to the above detailed preparation method, i.e. it does not mean that the present application must rely on the above detailed preparation method to be implemented. It should be understood by those skilled in the art that any improvement on the present application, equivalent replacement of each raw material of the product of the present application, addition of auxiliary ingredients, selection of specific methods, etc. all fall within the protection scope and disclosure scope of the present application.​

Claims

1. A phosphorus-carbon composite negative electrode material, characterized by, For a composite capsule structure, including porous carbon, ternary phosphide A loaded in the pore channel of the porous carbon x L 1-x M y P and a carbon coating layer; in the ternary phosphide A x L 1-x M y P, A is any one of Fe, Co and Ni, L is Ge or Sn, M is Se or Te, 0.1≤x≤0.5, 0.5≤y≤1.

5. 2.The phosphorus-carbon composite negative electrode material of claim 1, characterized in that, The ternary phosphide A x L 1-x M y A is Ni, L is Sn, and M is Se in P. 3.The phosphorus-carbon composite negative electrode material of claim 1, wherein, The ternary phosphide A x L 1-x M y P, 0.2≤x≤0.4, 0.8≤y≤1.

2.

4. The phosphorus-carbon composite negative electrode material of claim 1, wherein, The porous carbon has a pore volume of 0.6 to 1.5 m 3 / g, a specific surface area of 800 to 2100 m 2 / g, and a particle size D50 of 2 to 10 μm.

5. The phosphorus-carbon composite negative electrode material of claim 1, wherein, The phosphorus-carbon composite negative electrode material, the porous carbon accounts for 30wt%-50wt%, the ternary phosphide A x L 1-x M y P accounts for 50 wt%-70 wt%, and the rest is a carbon coating layer.

6. The method for producing the phosphorus-carbon composite negative electrode material according to any one of claims 1 to 5, characterized by, The method comprises the following steps: (S1) according to A x L 1-x M y P stoichiometric ratio, A salt, L salt are dissolved in a solvent to form a mixed solution; element A in A salt and porous carbon are added to porous carbon according to 1 mmol: (5-10) g, and A ion and L ion loaded porous carbon is obtained by immersion adsorption, centrifugal drying; (S2) reducing the A ion and the L ion by heat treating the porous carbon loaded with the A ion and the L ion in a reducing atmosphere, and obtaining the porous carbon loaded with the metal A and the metal L after cooling; (S3) A, L, M, P in stoichiometric ratio, the M source and the porous carbon loaded with metal A and metal L are mixed to obtain a mixture; the mixture and the phosphorus source are heat treated at 500-600 DEG C for 2-6 h; then, temperature control treatment is performed to obtain the porous carbon loaded with A, L, M, P x L 1-x M y P in stoichiometric ratio, the M source and the porous carbon loaded with metal A and metal L are mixed to obtain a mixture; the mixture and the phosphorus source are heat treated at 500-600 DEG C for 2-6 h; then, temperature control treatment is performed to obtain the porous carbon loaded with A, L, M, P x L 1-x M y P in stoichiometric ratio, the M source and the porous carbon loaded with metal A and metal L are mixed to obtain a mixture; the mixture and the phosphorus source are heat treated at (S4) A x L 1-x M y P-loaded porous carbon is carbon-coated by a gas-phase deposition method to obtain the phosphorus-carbon composite negative electrode material.

7. The preparation method according to claim 6, characterized in that, In step (S1), the A salt is a nitrate salt and / or a chloride salt of A, the L salt is a nitrate salt and / or a chloride salt of L, the solvent is at least one of ethanol, isopropanol and water, the amount ratio of the porous carbon to the mixed solution is 1 g:(10-20) mL, and the impregnation adsorption is 24-48 h.

8. The production method according to claim 6, characterized by, In step (S2), the reducing atmosphere comprises hydrogen, and the volume fraction of hydrogen is 5-20%; the heat treatment is performed at 300-600 ℃ for 3-6 h.

9. The production method according to claim 8, characterized by, The reducing atmosphere is a hydrogen-argon mixed atmosphere.

10. The method of claim 6, wherein, In step (S3), the total mole number of the A element in the A salt, the L element in the L salt and the M element in the M source is in a ratio of 1:(5-10) to the mole number of the P element in the P source; the P source is red phosphorus or a phosphide; and the phosphide is at least one of ammonium dihydrogen phosphate, sodium dihydrogen phosphate and triphenylphosphine.

11. Application of the phosphorus-carbon composite negative electrode material in any one of claims 1-5 in a lithium ion battery or a sodium ion battery.

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