阅读说明：本技术 一种二次电池及用电装置 (Secondary battery and power utilization device ) 是由 祝佳丽 姜斌 于哲勋 朱金保 刘宏勇 于 2021-08-18 设计创作，主要内容包括：本发明提供了一种二次电池及用电装置,在钠离子二次电池中增加补钠源,通过补钠源来补充钠离子电池在首次充放电过程中因形成负极SEI膜以及不可逆化合物而消耗掉一部分活性钠,还进一步限定补钠二次电池中负极极片的残钠含量W-(R),将该W-(R)设计在本发明限定范围内,避免了因补钠过多或过少而对电池综合性能造成的影响,使得添加的钠可以直接补充电池在首次充放电过程中因形成负极SEI膜以及不可逆化合物而消耗的活性钠,弥补了材料首次充放电的容量消耗,从而获得了综合性能较优的补钠二次电池,提升了电池的首次库伦效率、循环性能、存储性能。(The invention provides a secondary battery and an electric device, wherein a sodium supplement source is added in a sodium ion secondary battery, the sodium supplement source is used for supplementing a part of active sodium consumed by the sodium ion battery due to the formation of a negative electrode SEI film and an irreversible compound in the first charge-discharge process of the sodium ion battery, and the residual sodium content W of a negative electrode plate in the sodium supplement secondary battery is further limited R W is formed by R The design is in the limited range of the invention, the influence on the comprehensive performance of the battery caused by excessive or insufficient sodium supplement is avoided, so that the added sodium can directly supplement the active sodium consumed by the battery due to the formation of a negative electrode SEI film and an irreversible compound in the first charge-discharge process, the capacity consumption of the material in the first charge-discharge process is compensated, and the comprehensive performance is obtainedThe excellent sodium-supplementing secondary battery improves the first coulombic efficiency, the cycle performance and the storage performance of the battery.)

1. A secondary battery comprises a positive pole piece, a negative pole piece and an isolating membrane which is arranged between the positive pole piece and the negative pole piece at intervals, wherein the positive pole piece and/or the negative pole piece contain a sodium supplement source, and the secondary battery is characterized in that the residual sodium content of the negative pole piece is W_R(ii) a The residual sodium content W_RTaking the residual active sodium content W of the negative pole piece_R1And/or the residual absolute sodium content W of the negative pole piece_R2；

The content W of residual active sodium of the negative pole piece_R1First sodium removal per unit area of the negative electrode sheet/first sodium removal per unit area of the positive electrode sheet, W_R1The values of (b) satisfy the following ranges:

according to the general test method in the industry: w is not less than 0_R1≤62％；

Wherein the conditions of the universal test method in the industry are as follows: discharging the battery to the rated lower limit voltage, disassembling the battery, and taking out the positive and negative pole pieces; after a button cell is prepared by taking the negative pole piece as a working electrode and the sodium piece as a counter electrode, charging to 2.5V at a constant current of 50uA, and recording the charging capacity which is the first sodium removal amount of the negative pole piece in unit area; after a button cell is prepared by taking the positive pole piece as a working electrode and the sodium piece as a counter electrode, charging the button cell to 0.5V which exceeds the rated upper limit voltage of the secondary cell by a constant current of 50uA, and recording the charging capacity which is the first sodium removal amount of the unit area of the positive pole piece;

the residual absolute sodium content W of the negative pole piece_R2Negative electrode sheet absolute sodium content per unit area/positive electrodeAbsolute sodium content per unit area of tablet, W_R2The values of (b) satisfy the following ranges:

the testing method according to the national standard comprises the following steps: w is more than or equal to 20%_R2≤220％；

The national standard test method refers to the following steps: GB/T23367.2-2009 lithium cobaltate chemical analysis method part 2: and (3) measuring the amounts of lithium, nickel, manganese, magnesium, aluminum, iron, sodium, calcium and copper, discharging the battery to the rated lower limit voltage by adopting an inductively coupled plasma atomic emission spectrometry, disassembling the battery, taking out the positive and negative pole pieces, and carrying out ICP (inductively coupled plasma) test.

2. The secondary battery according to claim 1, further satisfying the following relational expression: mass coating ratio W_N/PCoating amount of negative electrode sheet per unit area of material/coating amount of positive electrode sheet per unit area of material, W_N/PThe value range of (a) is 0.13-2.06.

3. The secondary battery according to claim 1 or 2, characterized in that the following relational expression is also satisfied: coating thickness ratio of substance T_N/PNegative electrode sheet material coating thickness per unit area/positive electrode sheet material coating thickness per unit area, T_N/PThe value range of (A) is 0.16-5.72.

4. The secondary battery according to claim 1 or 2, wherein the sodium supplement source in the positive electrode plate is at least one of a binary sodium-containing compound, a ternary sodium-containing compound and an organic sodium salt; structure Na of the binary sodium-containing compound_xA, wherein x is more than 0 and less than or equal to 3, and A is at least one of O, P, F, S, Si, Sn or N; the structure Na of the ternary sodium-containing compound_xM_yN_zWherein x is more than or equal to 1 and less than or equal to 8, y is more than or equal to 1 and less than or equal to 6, z is more than or equal to 1 and less than or equal to 6, M is one or more metal elements of Fe, Co, Cu, Ni, Mn, Zr, Mg, Al, V, Ti and Mo, and N is one or more nonmetal elements of O, N, F, B, S; the organic sodium salt comprises Na₂DHBN，Na₂C₂O₄At least one of (1).

5. The secondary battery of claim 4, wherein the binary sodium-containing compound comprises Na₂O、Na₂O₂、NaF、Na₂S、Na₃At least one of N; the ternary sodium-containing compound comprises Na₄FeO₅，Na₆CoO₄，Na₂NiO₂，Na₅ReO₆，Na₂MnO₃，Na₂MoO₃，Na_0.65Ni_1.35O₂At least one of (1).

6. The secondary battery according to claim 1 or 2, wherein the sodium source in the negative electrode plate is supplemented by at least one of sodium belt sodium supplementation, sodium powder spraying sodium supplementation, sodium evaporation sodium supplementation, negative electrode solvent sodium supplementation and third electrode sodium supplementation.

7. The secondary battery according to claim 1, wherein the positive electrode active material in the positive electrode sheet comprises: a mixture of any one or more of a layered oxide, a polyanion compound, and prussian blue; wherein the layered oxide comprises Na_xMO₂，x>0, M ═ Ni, Co, Mn, or Fe; the polyanion compound is Na_xM_y(PO₄)_ZAnd/or Na₂A_h(SO₄)₂(H₂O)₂，x>0,y>0，z>0，h>0, M ═ Fe, V, or Mn, a is a transition metal; said Prussian blue comprises Na_xMM(CN)₆Wherein x is>0, MM ═ Fe, Co, Mn, or Ni.

8. The secondary battery of claim 1, wherein the negative active material in the negative electrode tab comprises a mixture of one or more negative electrodes of carbon-based materials, alloy materials, transition metal oxides, transition metal sulfides, phosphorus-based materials, or titanate materials.

9. The secondary battery of claim 1, further comprising an electrolyte comprising a sodium salt and a solvent.

10. An electric device comprising the secondary battery according to any one of claims 1 to 9.

Technical Field

The invention relates to the field of sodium ion batteries, in particular to a secondary battery and an electric device.

Background

The working principle of the sodium ion battery is similar to that of the lithium ion battery, and the charging and discharging are realized by utilizing the process that sodium ions are embedded and separated between a positive electrode and a negative electrode. Compared with the conventional lithium ion battery anode material, the sodium ion anode material has the advantages of abundant reserves, easily available raw materials and low cost, so that the sodium ion battery is concerned.

Meanwhile, the sodium ion battery has the same problem as the lithium ion battery, namely, when the battery is charged for the first time, an SEI film is formed on the surface of a negative electrode, a part of sodium ions are consumed, and the reversible capacity of the positive electrode is reduced; in the process of circulation and storage, sodium ions are continuously consumed to repair the continuously damaged negative electrode SEI film, so that active sodium is continuously consumed, and the irreversible loss of the battery capacity is further aggravated.

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

Disclosure of Invention

One of the objects of the present invention is: provides a secondary battery, which solves the problem that the battery capacity is reduced because a part of active sodium is consumed due to the formation of a negative SEI film and an irreversible compound in the first charge-discharge process of the prior sodium ion battery.

In order to achieve the purpose, the invention adopts the following technical scheme:

a secondary battery comprises a positive pole piece, a negative pole piece and an isolating membrane arranged between the positive pole piece and the negative pole piece at intervals, wherein the positive pole piece and/or the negative pole piece contain a sodium supplement source, and the residual sodium content of the negative pole piece is W_R(ii) a The residual sodium content W_RTaking the residual active sodium content W of the negative pole piece_R1And/or the residual absolute sodium content W of the negative pole piece_R2；

The content W of residual active sodium of the negative pole piece_R1First sodium removal per unit area of the negative electrode sheet/first sodium removal per unit area of the positive electrode sheet, W_R1The values of (b) satisfy the following ranges:

according to the general test method in the industry: w is not less than 0_R1≤62％；

Wherein the conditions of the universal test method in the industry are as follows: discharging the battery to the rated lower limit voltage (namely, in a complete discharge state), disassembling the battery, and taking out the positive and negative pole pieces; after a button cell is prepared by taking the negative pole piece as a working electrode and the sodium piece as a counter electrode, charging to 2.5V at a constant current of 50uA, and recording the charging capacity which is the first sodium removal amount of the negative pole piece in unit area; after a button cell is prepared by taking the positive pole piece as a working electrode and the sodium piece as a counter electrode, charging the button cell to 0.5V which exceeds the rated upper limit voltage of the secondary cell by a constant current of 50uA, and recording the charging capacity which is the first sodium removal amount of the unit area of the positive pole piece;

the residual absolute sodium content W of the negative pole piece_R2Absolute sodium content per unit area of negative electrode sheet/absolute sodium content per unit area of positive electrode sheet, W_R2The values of (b) satisfy the following ranges:

the testing method according to the national standard comprises the following steps: w is more than or equal to 20%_R2≤220％；

The national standard test method refers to the following steps: GB/T23367.2-2009 lithium cobaltate chemical analysis method part 2: and (3) measuring the amounts of lithium, nickel, manganese, magnesium, aluminum, iron, sodium, calcium and copper, discharging the battery to the rated lower limit voltage (namely in a complete discharge state) by adopting an inductively coupled plasma atomic emission spectrometry, disassembling the battery, taking out the positive and negative pole pieces, and carrying out ICP test.

Preferably, the secondary battery further satisfies the following relational expression: mass coating ratio W_N/PCoating amount of negative electrode sheet per unit area of material/coating amount of positive electrode sheet per unit area of material, W_N/PThe value range of (a) is 0.13-2.06.

Preferably, the secondary battery further satisfies the following relational expression: coating thickness ratio of substance T_N/PNegative electrode sheet material coating thickness per unit area/positive electrode sheet material coating thickness per unit area, T_N/PThe value range of (A) is 0.16-5.72.

Preferably, the sodium supplement source in the positive pole piece is at least one of a binary sodium-containing compound, a ternary sodium-containing compound and an organic sodium salt; structure Na of the binary sodium-containing compound_xA, wherein x is more than 0 and less than or equal to 3, and A is at least one of O, P, F, S, Si, Sn or N; the structure Na of the ternary sodium-containing compound_xM_yN_zWherein x is more than or equal to 1 and less than or equal to 8, y is more than or equal to 1 and less than or equal to 6, z is more than or equal to 1 and less than or equal to 6, M is one or more metal elements of Fe, Co, Cu, Ni, Mn, Zr, Mg, Al, V, Ti and Mo, and N is one or more nonmetal elements of O, N, F, B, S; the organic sodium salt comprises Na₂DHBN，Na₂C₂O₄At least one of (1).

Preferably, the binary sodium-containing compound comprises Na₂O、Na₂O₂、NaF、Na₂S、Na₃At least one of N; the ternary sodium-containing compound comprises Na₄FeO₅，Na₆CoO₄，Na₂NiO₂，Na₅ReO₆，Na₂MnO₃，Na₂MoO₃，Na_0.65Ni_1.35O₂At least one of (1).

Preferably, the sodium supplementing mode of the sodium supplementing source in the negative electrode plate is at least one of sodium band sodium supplementing, sodium powder spraying sodium supplementing, sodium supplementing by evaporation, negative electrode solvent sodium supplementing and third electrode sodium supplementing.

Preferably, the positive electrode active material in the positive electrode sheet includes: any one or more of a layered oxide, a polyanion compound and prussian blueMixing; wherein the layered oxide comprises Na_xMO₂，x>0, M ═ Ni, Co, Mn, or Fe; the polyanion compound is Na_xM_y(PO₄)_ZAnd/or Na₂A_h(SO₄)₂(H₂O)₂，x>0,y>0，z>0，h>0, M ═ Fe, V, or Mn, a is a transition metal; said Prussian blue comprises Na_xMM(CN)₆Wherein x is>0, MM ═ Fe, Co, Mn, or Ni.

Preferably, the negative active material in the negative electrode sheet comprises one or more negative electrode mixtures of carbon-based materials, alloy materials, transition metal oxides, transition metal sulfides, phosphorus-based materials or titanate materials.

Preferably, the secondary battery further includes an electrolyte including a sodium salt and a solvent. Wherein the sodium salt may be Na₂DHBN、Na₂C₂O₄And the like.

It is a second object of the present invention to provide an electric device including the secondary battery of any one of the above.

Compared with the prior art, the invention has the beneficial effects that:

1) the sodium supplement source is added in the sodium ion secondary battery, the sodium supplement source is used for supplementing a part of active sodium consumed by the sodium ion battery due to the formation of a negative electrode SEI film and an irreversible compound in the first charge-discharge process of the sodium ion battery, and the residual sodium content W of a negative electrode plate in the sodium supplement secondary battery is further limited_RW is formed by_RThe design is in the limited range of the invention, the influence on the comprehensive performance of the battery caused by excessive or insufficient sodium supplement is avoided, so that the added sodium can directly supplement the active sodium consumed by the battery due to the formation of a negative electrode SEI film and an irreversible compound in the first charge-discharge process, the capacity consumption of the material in the first charge-discharge process is compensated, the sodium supplement secondary battery with better comprehensive performance is obtained, and the first coulombic efficiency, the cycle performance and the storage performance of the battery are improved. In addition, the sodium content regulation and control of the invention can also supplement the continuous damage and repair of an SEI film in the battery circulation and storage processesThe consumed active sodium further improves the comprehensive performance of the battery.

2) In addition, the invention also reasonably designs the material coating quantity ratio of the positive and negative pole pieces and the residual sodium content W of the negative pole piece_RBy supplementing each other, the added sodium not only directly supplements the active sodium consumed in the first charging and discharging process, but also supplements the active sodium consumed in the battery circulation and storage process due to the fact that the SEI film is continuously damaged and repaired, and makes up the irreversible capacity loss in the first charging and discharging process of the material and the sodium continuous consumption loss in the circulation process, so that the comprehensive performance of the battery is further improved.

3) In addition, the invention also reasonably designs the material thickness ratio of the positive and negative pole pieces, the material coating amount ratio of the positive and negative pole pieces and the residual sodium content W of the negative pole piece_RThe sodium supplement amount of the battery is more reasonable through comprehensive regulation and control of the three components, so that the comprehensive performance of the battery is improved to be better.

Detailed Description

The invention provides a secondary battery, which comprises a positive pole piece, a negative pole piece and an isolating membrane arranged between the positive pole piece and the negative pole piece at intervals, wherein the positive pole piece and/or the negative pole piece contain a sodium supplement source, and the content of residual sodium of the negative pole piece is W_R(ii) a The residual sodium content W_RTaking the residual active sodium content W of the negative pole piece_R1And/or the residual absolute sodium content W of the negative pole piece_R2；

The content W of residual active sodium of the negative pole piece_R1First sodium removal per unit area of the negative electrode sheet/first sodium removal per unit area of the positive electrode sheet, W_R1The values of (b) satisfy the following ranges:

according to the general test method in the industry: w is not less than 0_R1≤62％；

Wherein the conditions of the universal test method in the industry are as follows: discharging the battery to the rated lower limit voltage (namely, in a complete discharge state), disassembling the battery, and taking out the positive and negative pole pieces; after a button cell is prepared by taking the negative pole piece as a working electrode and the sodium piece as a counter electrode, charging to 2.5V at a constant current of 50uA, and recording the charging capacity which is the first sodium removal amount of the negative pole piece in unit area; after a button cell is prepared by taking the positive pole piece as a working electrode and the sodium piece as a counter electrode, charging the button cell to 0.5V which exceeds the rated upper limit voltage of the secondary cell by a constant current of 50uA, and recording the charging capacity which is the first sodium removal amount of the unit area of the positive pole piece;

the residual absolute sodium content W of the negative pole piece_R2Absolute sodium content per unit area of negative electrode sheet/absolute sodium content per unit area of positive electrode sheet, W_R2The values of (b) satisfy the following ranges:

the testing method according to the national standard comprises the following steps: w is more than or equal to 20%_R2≤220％；

The national standard test method refers to the following steps: GB/T23367.2-2009 lithium cobaltate chemical analysis method part 2: and (3) measuring the amounts of lithium, nickel, manganese, magnesium, aluminum, iron, sodium, calcium and copper, discharging the battery to the rated lower limit voltage (namely in a complete discharge state) by adopting an inductively coupled plasma atomic emission spectrometry, disassembling the battery, taking out the positive and negative pole pieces, and carrying out ICP test.

Preferably, according to an industry-wide test method, the content W of the residual active sodium of the negative pole piece_R1The values of (A) are as follows: w is not less than 0_R1≤60％；

According to the national standard test method, the residual absolute sodium content W of the negative pole piece_R2The values of (A) are as follows: w is more than or equal to 20%_R2≤180％。

Further preferably, according to an intra-industry general test method, the content W of the residual active sodium of the negative pole piece_R1The values of (A) are as follows: w is not less than 0_R1≤56％；

According to the national standard test method, the residual absolute sodium content W of the negative pole piece_R2The values of (A) are as follows: w is more than or equal to 20%_R2≤120％。

During the sodium supplement process of the battery, two sodium supplement situations are included, the first is to supplement the sodium amount consumed by the first SEI film formed on the negative electrode and the irreversible compound, and the second is to supplement the sodium amount lost by the continuous consumption and repair of the SEI film in the circulation and storage processes. And adopting the common test method W in the industry_R1The case of 0 means that sodium is supplemented only to the negative electrode headThe sodium quantity consumed by the SEI film and the irreversible compound is formed for the second time, and the sodium quantity consumed in the circulating and storing process is not supplemented, so that the first sodium removal quantity CAP of the unit area of the negative pole piece detected by a common test method in the industry is adopted_NIs 0, i.e., W_R1In the case of 0, W is obtained by adopting a national standard test method_R2A difference of 0 may be inversely demonstrated to supplement only the amount of sodium that is consumed for the first negative electrode to form the SEI film and for the irreversible compound.

Further, the secondary battery also satisfies the following relational expression: mass coating ratio W_N/PCoating amount W of negative electrode sheet per unit area_NCoating amount W of substance per unit area of positive electrode plate_P，W_N/PThe value range of (a) is 0.13-2.06. The inventor further discovers that the content W of residual sodium in the negative pole piece is W through a large number of experiments_ROn the basis of the limitation, the coating amount ratio of the substance is limited, and the sodium supplement amount can be further controlled in a proper range, so that the sodium supplement secondary battery with better comprehensive performance is obtained. After the content of residual sodium in the negative pole piece and the coating amount ratio of substances are limited, compared with the conventional sodium supplement design, the coating amount of the negative pole is larger, so that the negative pole has more sodium storage point positions for storing more active sodium provided by the positive pole/negative pole sodium-containing source, the sodium supplement amount is increased to a greater extent, and various performances of the battery are improved. Generally, the mass coating amount ratio W_N/PThe larger the coating amount W of the negative electrode plate per unit area_NThe larger the anode can store more additional sodium, and the larger the residual sodium content in the anode sheet. Specifically, the material coating amount ratio W_N/PThe range of the value of (a) can be 0.13-0.53, 0.53-0.63, 0.63-0.73, 0.73-0.83, 0.83-0.93, 0.93-1.03, 1.03-1.33, 1.33-1.53, 1.53-1.73, 1.73-2.06.

Further, the secondary battery also satisfies the following relational expression: coating thickness ratio of substance T_N/PCoating thickness T of negative pole piece per unit area_NCoating thickness T of material per unit area of positive pole piece_P，T_N/PThe value range of (A) is 0.16-5.72. Coating thickness of matterThe coating thickness can be obtained by dividing the coating amount by the compacted density and regulating the compacted density after the coating amount is determined. The coating thickness ratio of the substances defined by the invention is that the coating thicknesses of the positive and negative pole pieces are proper, the positive and negative poles have smaller interface contact resistance, and the sodium ions are more smoothly inserted and removed. The inventor further discovers that the content W of residual sodium in the negative pole piece is W through a large number of experiments_RMass coating ratio W_N/POn the basis of the limitation of (2), coating the substance with a thickness ratio T_N/PFurther limitation is made, the regulation and control of the sodium supplement amount are better, and the sodium supplement secondary battery with the optimal comprehensive performance can be obtained. In particular, the material coating thickness ratio T_N/PThe range of the value of (a) can be 0.16-0.22, 0.22-0.32, 0.32-0.42, 0.42-0.52, 0.52-0.62, 0.62-0.72, 0.72-0.82, 0.82-0.92, 0.92-1.22, 1.22-1.52, 1.52-1.82, 1.82-2.02, 2.02-2.30, 2.30-2.62, 2.62-3.02, 3.02-3.52, 3.52-3.82, 3.82-4.22, 4.22-4.82, 4.82-5.32, 5.32-5.72.

When the residual sodium content W of the negative pole piece_RMass coating ratio W_N/PMaterial coating thickness ratio T_N/PThe three control the time simultaneously, the design idea can be: determining the residual active sodium content W of the battery according to the requirements of actual battery cycle and storage performance_R1And/or residual absolute sodium content W_R2Therefore, the vacant sodium storage point positions of the negative electrode relative to the positive electrode which need to be designed more can be calculated; then, the coating ratio W of the anode and cathode materials is calculated_N/P. Meanwhile, according to the actual process capability, a reasonable coating amount of the negative electrode is given, and a corresponding coating amount of the positive electrode can be obtained; then, by comprehensively evaluating the material characteristics and the cell performance of the anode and cathode materials and giving the compaction density of the anode and cathode materials, the coating thickness of the anode and cathode can be converted, namely, the coating thickness ratio T of the substance is determined_N/P。

Further, the sodium supplement source in the positive pole piece is at least one of a binary sodium-containing compound, a ternary sodium-containing compound and an organic sodium salt; structure Na of the binary sodium-containing compound_xA, wherein x is more than 0 and less than or equal to 3, and A is at least one of O, P, F, S, Si, Sn or N; the above-mentionedStructure Na of ternary sodium-containing compound_xM_yN_zWherein x is more than or equal to 1 and less than or equal to 8, y is more than or equal to 1 and less than or equal to 6, z is more than or equal to 1 and less than or equal to 6, M is one or more metal elements of Fe, Co, Cu, Ni, Mn, Zr, Mg, Al, V, Ti and Mo, and N is one or more nonmetal elements of O, N, F, B, S; the organic sodium salt comprises Na₂DHBN，Na₂C₂O₄At least one of (1). Further preferably, the binary sodium-containing compound comprises Na₂O、Na₂O₂、NaF、Na₂S、Na₃At least one of N; the ternary sodium-containing compound comprises Na₄FeO₅，Na₆CoO₄，Na₂NiO₂，Na₅ReO₆，Na₂MnO₃，Na₂MoO₃，Na_0.65Ni_1.35O₂At least one of (1).

Further, the sodium supplementing mode of the sodium supplementing source in the negative electrode plate is at least one of sodium band sodium supplementing, sodium powder spraying sodium supplementing, sodium supplementing by evaporation, negative electrode solvent sodium supplementing and third electrode sodium supplementing.

Further, the positive electrode active material in the positive electrode sheet includes: a mixture of any one or more of a layered oxide, a polyanion compound, and prussian blue; wherein the layered oxide comprises Na_xMO₂，x>0, M ═ Ni, Co, Mn, or Fe; the polyanion compound is Na_xM_y(PO₄)_ZAnd/or Na₂A_h(SO₄)₂(H₂O)₂，x>0,y>0，z>0，h>0, M ═ Fe, V, or Mn, a is a transition metal; said Prussian blue comprises Na_xMM(CN)₆Wherein x is>0, MM ═ Fe, Co, Mn, or Ni.

Further, the negative active material in the negative electrode sheet comprises one or more negative electrode mixtures of carbon-based materials, alloy materials, transition metal oxides, transition metal sulfides, phosphorus-based materials or titanate materials.

Further, the secondary battery further includes an electrolyte,the electrolyte includes a sodium salt and a solvent. Wherein the sodium salt may be Na₂DHBN、Na₂C₂O₄And the like. The solvent can be similar to the solvent of the lithium ion battery, and can be cyclic carbonate, including PC and EC; or chain carbonates including DFC, DMC, or EMC; and also carboxylic acid esters including MF, MA, EA, MP, etc. In addition, the electrolyte may further include additives, and the additives include, but are not limited to, at least one of film forming additives, conductive additives, flame retardant additives, anti-overcharge additives, additives for improving low-temperature performance, and multifunctional additives.

Further, the separator used in the secondary battery may be various materials suitable for a separator of a lithium ion battery in the art, and for example, may be one or a combination of more of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, natural fiber, and the like, including but not limited thereto.

Another aspect of the present invention provides an electric device including the secondary battery described in any one of the above.

The electric device can be a vehicle, a mobile phone, a portable device, a notebook computer, a ship, a spacecraft, an electric toy, an electric tool and the like. The vehicle can be a fuel oil vehicle, a gas vehicle or a new energy vehicle, and the new energy vehicle can be a pure electric vehicle, a hybrid electric vehicle or a range-extended vehicle and the like; spacecraft include aircraft, rockets, space shuttles, and spacecraft, among others; electric toys include stationary or mobile electric toys, such as game machines, electric car toys, electric ship toys, electric airplane toys, and the like; the electric power tools include metal cutting electric power tools, grinding electric power tools, assembly electric power tools, and electric power tools for railways, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, electric impact drills, concrete vibrators, and electric planers.

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

According to the following test method, the sodium-supplementing secondary battery of the invention is disassembled and various performances thereof are tested.

Firstly, according to the specification of the battery, the rated capacity of the battery is set to be C₀Upper limit voltage V of rated charge of battery_URated charge cutoff current I of battery₀Rated discharge lower limit voltage V of battery_L(ii) a Then, the anode and cathode pole pieces are pretreated according to the following method:

1) adjusting the battery to 0% SOC: taking the battery, and firstly taking the current as 1 to obtain the rated capacity C of the battery₀Discharging to the rated lower limit voltage V of the battery_L(ii) a Standing for 5 min; then the rated capacity C of the battery is set to 0.1₀Discharging to the rated lower limit voltage V of the battery_L；

2) Disassembling the 0% SOC battery: disassembling the battery in a glove box filled with argon to obtain a positive pole piece and a negative pole piece in a 0% SOC state;

3) cleaning a pole piece: cleaning the pole pieces in a glove box filled with argon, and respectively soaking the positive pole piece and the negative pole piece in a 0% SOC state in a fresh DMC solution for 30 min; taking out, and cleaning the surface with alcohol;

4) naturally drying the pole piece: and naturally drying for 24 hours in a glove box filled with argon to obtain the anode pole piece and the cathode pole piece to be detected.

Then, the residual sodium content W of the negative pole piece is measured_R1&W_R2Mass coating ratio W_N/PMaterial coating thickness ratio T_N/PSpecific tests were performed.

Residual sodium content W of first and negative pole pieces_RTesting

1.1 according to the general method of industry, the content W of residual active sodium of the negative pole piece_R1The specific process of the test is as follows:

1) test 0% SOC negative pole piece unit area first sodium removal CAP_N: taking the negative plate air-dried by 0% of SOC, and erasing the powder on the single surface; selecting regions with uniform thickness, and punching to obtain a region with an area S by using a punching machine₀The small disks of (a); then assembling a button cell in a glove box filled with argon. Wherein the negative tiny disc is one pole of the button cell, the pure sodium disc is a counter electrode, and the assembly process is a conventional button cell process. After the assembled button cell is kept stand for 6 hours, the button cell is loaded to a test cabinet with charge and discharge capacity, and a test flow is sent; the test flow is as follows: charging to 2.5V with a constant current of 50uA, recording the charging capacity displayed by the test cabinet, and recording as 0% of the first sodium removal CAP of the SOC negative pole piece in unit area_N。

2) Test 0% SOC positive pole piece unit area first sodium removal CAP_P: taking the positive plate air-dried by 0% of SOC, and erasing single-side powder; selecting regions with uniform thickness, and punching to obtain a region with an area S by using a punching machine₀The small disks of (a); and assembling the button cell in a glove box filled with argon. Wherein the anode small wafer is one electrode of the button cell, the pure sodium wafer is a counter electrode, and the assembly process is a conventional button cell process. After the assembled button cell is kept stand for 6 hours, the button cell is loaded to a test cabinet with charge and discharge capacity, and a test flow is sent; the test flow comprises the following steps: charging to battery rated upper limit voltage (V) with 50uA current_U+0.5V), recording the charging capacity displayed by the test cabinet, and recording as 0% of the initial sodium removal capacity CAP of the unit area of the SOC positive pole piece_P。

3) Residual active sodium content W of negative pole piece_R1Initial sodium removal CAP of unit area of 0% SOC negative pole piece_N0% SOC positive pole piece unit area first sodium removal CAP_P。

1.2 according to the national standard test method, refer to the national standard test method GB/T23367.2-2009 lithium cobaltate chemical analysis method part 2: measuring the amount of lithium, nickel, manganese, magnesium, aluminum, iron, sodium, calcium and copper, adopting an inductively coupled plasma atomic emission spectrometry to discharge the battery to the rated lower limit voltage (namely in a complete discharge state), disassembling the battery, taking out a positive electrode plate and a negative electrode plate, carrying out ICP test, and measuring the residual absolute sodium content W of the negative electrode plate_R2The specific process of the test is as follows:

1) ICP test conditions for setting the content of metallic Na:

the test conditions for ICP are:

plasma flow rate: 15L/min;

auxiliary flow rate: 0.3L/min;

flow rate of the atomizer: 0.6L/min;

radio frequency power: 1300W;

sample flow rate: 1.5L/min;

the number of repetitions: 1;

observation direction: radial direction;

2) preparing a standard sample solution of Na: directly purchasing national or industry standard solutions, wherein the concentration is 1000 ug/mL; taking 10mL of standard solution to a 100mL volumetric flask, adding 2mL of 2% nitric acid, adding pure water for dilution to a scale, and shaking up for later use; taking 5 volumetric flasks, and preparing sample standard solutions with the concentrations of 0ug/mL, 0.25ug/mL, 0.5ug/mL, 1.0ug/mL and 2.5ug/mL by using the diluted standard solutions respectively; after the ICP testing equipment is stable, establishing a standard working curve of the element Na according to the testing conditions of 1), wherein the correlation coefficient of the standard working curve is more than or equal to 0.9995, and otherwise, re-preparing the standard solution until the standard coefficient of the curve meets the requirements;

3) preparing a solution of a sample to be tested: taking the area after air drying as S₀0% SOC negative pole piece&0% SOC Positive Pole piece, weighing, and recording weight as m_N、m_PEnsuring the weight to be 0.35-0.50g (accurate to 0.1 mg); adding analytically pure hydrochloric acid&Nitric acid and deionized water, heating on an electric hot plate for 10min, cooling, and diluting to 100ml (ensuring Na element solubility of sample to be tested in standard curve; if the solubility is not determined, testing first, if the concentration exceeds standard, then further diluting)

4) Analysis of the sample to be tested: testing a sample to be analyzed under the test conditions of 1), and respectively calculating 0% SOC negative pole piece by using an ICP device&Na element concentration C in 0% SOC positive pole piece_N、C_P(ii) a Then converting into area S according to formula₀Weight of pole piece Na;

wherein, the conversion formula is:

0% SOC negative pole piece Na weight M_N＝C_N*m_NDilution factor/1000000/2;

na weight M of 0% SOC positive pole piece_P＝C_P*m_PDilution factor/1000000/2;

absolute Na content CAP of 0% SOC unit area single-sided negative pole piece_N＝C_N*m_NDilution factor 26801/1000000/S₀/23/2。

Absolute Na content CAP of 0% SOC unit area single-sided positive pole piece_P＝C_P*m_PDilution factor 26801/1000000/S₀/23/2。

Residual absolute sodium content W of negative pole piece_R20% SOC negative pole piece unit area absolute sodium content CAP_NPer 0% SOC positive pole piece unit area absolute sodium content CAP_P。

Second, the material coating amount ratio W_N/PTesting

Taking the area as S_P0% SOC positive electrode sheet with area S_NWeighing the 0% SOC negative pole piece to obtain the weight M of the positive pole piece_PWeight M of negative electrode sheet_N(ii) a And then removing powder on the surfaces of the positive and negative electrode plates, wiping the positive electrode plate by adopting alcohol, and wiping the negative electrode plate by adopting deionized water to obtain the positive and negative electrode foils. Test area of S_PPositive electrode foil weight m_PArea is S_NWeight m of negative electrode foil_N. And calculating to obtain: coating amount W of substance per unit area of positive electrode plate_P＝(M_P-m_P)/S_P(ii) a Coating amount W of negative electrode sheet per unit area_N＝(M_N-m_N)/S_N。

Then, the material coating amount ratio W_N/PCoating amount W of negative electrode sheet per unit area_NCoating amount W of substance per unit area of positive electrode plate_P。

Third, the material coating thickness ratio T_N/PTesting

Taking 0% SOC positive and negative electrode plates after air drying, and measuring the thickness by a ten-thousandth ruler; recording the thickness t of the positive pole piece_PThickness t of negative electrode plate_N(ii) a And then removing powder on the surfaces of the positive and negative electrode plates, wiping the positive electrode plate by adopting alcohol, and wiping the negative electrode plate by adopting deionized water to obtain the positive and negative electrode foils. Testing the foil thickness with ten-thousandth micrometer, and recording the thickness of the anode foil as t_P1Negative electrodeThickness t of foil_N1. And calculating to obtain: coating thickness T of negative plate_N＝t_N-t_N1(ii) a Coating thickness T of positive plate_P＝t_P–t_P1。

Then, the material coating thickness ratio T_N/PCoating thickness T of negative pole piece per unit area_NCoating thickness T of material per unit area of positive pole piece_P。

In some of the embodiments, the sodium-supplementing secondary battery is a positive electrode sodium-supplementing secondary battery, and the positive electrode active material is P₂Form Na_0.72(Na_0.24Mn_0.76)O₂The cathode material is hard carbon, the diaphragm is a polyolefin membrane which is conventionally used in the industry, and the electrolyte is also conventionally used in sodium ion batteries in the industry. The test results are shown in tables 1-2.

TABLE 1

The data in Table 1 are converted into the residual sodium content W of the negative electrode sheet_RMass coating ratio W_N/PAnd material coating thickness ratio T_N/PAnd the comprehensive performance of the corresponding secondary battery was measured, and the results are shown in table 2.

TABLE 2

As can be seen from the detection results of the embodiments 1 to 6, in the sodium supplement of the positive pole piece, the content W of the residual sodium of the negative pole piece is reasonably regulated and controlled_RThe cycle life of the sodium supplement battery and the storage performance at 60 ℃ can be effectively improved at the same time. The reason is that the reasonable sodium supplement content control can not only compensate the capacity loss of the material in the first charge and discharge, but also advanceA portion of the extra sodium is stored in the material to make up for the sodium consumption during recycling and storage.

The test result also shows that the cycle performance and the storage performance of the battery can be further improved along with the improvement of the content of the residual sodium of the negative pole piece. However, the more the content of the residual sodium in the negative electrode plate is, the better the content of the residual sodium in the negative electrode plate is, when the content of the residual sodium in the negative electrode plate exceeds the limited range of the invention, that is, the sodium supplement amount is too much, the risk of sodium precipitation of the battery can be caused, and the use safety of the battery can not be ensured. At present, as the requirement of the power battery on the energy density is higher and higher, in order to meet the requirement of the energy density, the whole performance advantage of the battery can be ensured by properly sacrificing part of the cycle and storage performances.

In some embodiments, the sodium supplement of the negative electrode of the sodium secondary battery is carried out in a sodium band sodium supplement mode, and the positive active material is P₂Form Na_0.72(Na_0.24Mn_0.76)O₂The cathode material is hard carbon, the diaphragm is a polyolefin membrane which is conventionally used in the industry, and the electrolyte is also conventionally used in sodium ion batteries in the industry. The test results are shown in tables 3-4.

TABLE 3

The data in Table 3 were converted into the residual sodium content W of the negative electrode sheet_RMass coating ratio W_N/PAnd material coating thickness ratio T_N/PAnd the comprehensive performance of the corresponding secondary battery was measured, and the results are shown in table 4.

TABLE 4

From the test results of examples 7-10, it can be seen that in the sodium supplement of the negative pole piece, the content W of the residual sodium of the negative pole piece is regulated and controlled_RThe method can also play a role in simultaneously prolonging the cycle life of the sodium supplement battery and improving the storage performance at 60 ℃.

In addition, from the comparison between example 1 and example 7, it can be seen that when sodium is supplemented to the negative electrode sheet, the residual absolute sodium content W of the negative electrode sheet in example 7 is_R2In the case of smaller size, the battery obtained was superior in performance to the sodium-supplemented battery of example 1. This is mainly because the negative electrode plate is directly supplemented with sodium, and the negative electrode plate has more sodium storage sites, and can store more active sodium provided by the negative electrode sodium-containing source, so that the effect of larger sodium supplement amount in embodiment 1 can be achieved when the sodium supplement amount is smaller.

In addition, as can be seen from the comparison of examples 1 to 10, no matter the sodium is supplemented to the positive pole piece or the negative pole piece, when the residual sodium content W of the negative pole piece is regulated and controlled simultaneously_RMass coating ratio W_N/PMaterial coating thickness ratio T_N/PIn three cases, the performance of the sodium-supplementing secondary battery can be better, as compared with examples 9 and 10, the content W of the residual active sodium of the negative electrode plate_R1Not much different, and W in example 10_RYet less than W in example 9_RHowever, the cycle life and the storage performance at 60 ℃ of the corresponding sodium-supplemented secondary battery are better than those of the battery in example 9 according to the test results. It can be seen from this that the substance coating amount ratio W_N/PMaterial coating thickness ratio T_N/PAnd also has an influence on the performance of the sodium-supplement secondary battery.

In summary, when the residual sodium content W of the negative electrode plate is regulated and controlled at the same time_RMass coating ratio W_N/PMaterial coating thickness ratio T_N/PWhen the three are within the range, the negative electrode can additionally store more sodium under the condition of not separating sodium, the sodium quantity which is required to be consumed by the SEI film and the irreversible compound formed on the negative electrode can be supplemented, and the sodium quantity which is consumed in the subsequent circulation process can be supplemented, so that the sodium-supplementing secondary battery with better comprehensive performance is obtained, the problem that the battery capacity is reduced because a part of active sodium is consumed in the first charge and discharge process of the conventional sodium-ion battery due to the formation of the SEI film and the irreversible compound on the negative electrode is solved, the sodium supplementing quantity is better controlled, and the comprehensive performance of the secondary battery after sodium supplementation is effectively improved.

Variations and modifications to the above-described embodiments may also occur to those skilled in the art, which fall within the scope of the invention as disclosed and taught herein. Therefore, the present invention is not limited to the above-mentioned embodiments, and any obvious improvement, replacement or modification made by those skilled in the art based on the present invention is within the protection scope of the present invention. Furthermore, although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.