Negative-electrode-free electrode preparation and activation complete method based on dendritic silicon coating

Abstract

The invention relates to a complete method for preparing and activating a non-negative electrode based on a dendritic silicon coating. The micron-sized three-dimensional dendritic silicon composite coating is constructed on the surface of the copper foil current collector, and an asymmetric activation method of'low-rate charging-high-rate discharging 'is used in the whole battery, so that silicon is kept in an incomplete lithium removal state in circulation, and a stable interface layer rich in silicon-lithium alloy is formed in situ and dynamically maintained on the surface of the current collector. The dynamic interface layer can continuously provide rich lithium-philic nucleation sites and remarkably reduce nucleation and growth overpotential of lithium deposition, so that uniform and compact deposition of lithium is guided, generation of lithium dendrites and dead lithium is inhibited fundamentally, and the cycle life and safety of the negative-electrode-free lithium battery are greatly improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of lithium batteries, and particularly relates to a dendritic silicon coating electrode for a negative electrode-free lithium battery, a preparation method thereof, a coordinated asymmetric electrochemical activation method, and a corresponding negative electrode-free lithium battery. BACKGROUND

[0002] To break through the energy density bottleneck of traditional lithium-ion batteries, negative electrode-free lithium batteries have attracted much attention due to their ability to achieve a theoretical energy density of more than 450 Wh·kg -1 However, its development still faces the following challenges: the surface of the copper current collector has "lithium-phobicity", resulting in a high nucleation barrier for lithium deposition and uneven distribution, which easily grows dendrites and forms "dead lithium", causing rapid capacity decay and serious safety hazards.

[0003] To address the above challenges, existing regulation strategies are divided into two categories: surface modification and electrochemical process optimization, both of which have significant limitations: in terms of surface modification, CN117199254A discloses a conductive carbon coating containing silicon and tin nanoparticles, but nano-silicon has high cost and large volume expansion, and is easily pulverized and detached during cycling; CN118888762A proposes a "polymer film layer / multi-walled carbon lithiumophilic layer" composite current collector, in which the non-conductive polymer layer increases the internal resistance and non-active weight, and the multi-walled carbon layer relies on a complex magnetron sputtering process. Such solutions construct a static initial interface, which is difficult to cope with dynamic failure in cycling. In terms of process optimization, CN118399525A dynamically adjusts the discharge cutoff voltage through a three-electrode system, which is complex and does not combine with material properties; CN120049031A uses a low-temperature large-current formation method, which is harsh in process control and only works on the initial state, lacking coordination with interface structure evolution. Such strategies are independent of electrode material design, lacking long-term coordination with interface structure evolution.

[0004] It is worth noting that micro-silicon materials with three-dimensional dendritic or porous structures can effectively buffer volume expansion due to their pores, and have been studied in the field of traditional lithium-ion batteries, such as the porous silicon / polyaniline composite anode disclosed in CN111668457A and the amorphous copper-coated spherical porous silicon composite material disclosed in CN120413653A. However, the application of such micro-silicon materials in negative electrode-free lithium battery systems and the design of matching electrochemical processes have not been reported to date.

[0005] Therefore, it is of great significance to develop a negative electrode-free lithium battery technology that can dynamically coordinate the properties of micro-silicon materials with electrochemical processes and achieve long-term stability of the interface. SUMMARY

[0006] The present application aims to overcome the bottleneck of short cycle life, uneven lithium deposition and poor safety in existing anode-free lithium batteries. The core of the present application is that a micron-sized dendritic silicon composite functional coating with a specific structure is dynamically coordinated with an asymmetric electrochemical activation process to in-situ construct and dynamically maintain a stable interface layer of Si(0 x (x < 3.75) alloy in the coating during battery cycling. This alloy layer can provide abundant lithiumophilic nucleation sites and significantly reduce the lithium deposition overpotential, thereby continuously guiding uniform and dense lithium deposition and fundamentally inhibiting dendrites and "dead lithium".

[0007] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0008] In a first aspect, the present application provides a dendritic silicon-based composite anode sheet and a preparation method thereof.

[0009] The anode sheet comprises a copper foil current collector and a composite functional coating arranged on the surface thereof. The coating comprises an active component, a binder and a conductive agent.

[0010] The active component is micron-sized dendritic silicon with a particle size D50 of 1-20 μm and a porosity of 15%-50%. In the coating, the mass fraction of the dendritic silicon is 10%-90% based on the total mass.

[0011] The binder system comprises a first binder and a second binder. The first binder is styrene-butadiene rubber, and the mass fraction thereof is fixed at 0.5%-5% based on the total mass of the composite coating. The second binder is selected from at least one of sodium alginate, sodium carboxymethyl cellulose and polyacrylic acid. The total mass fraction of the binder is 5%-30%.

[0012] The conductive agent system comprises a first conductive agent and a second conductive agent. The first conductive agent is conductive carbon black, and the mass fraction thereof is 2%-20% based on the total mass of the composite coating. The second conductive agent is selected from at least one of acetylene black, carbon nanotube, graphene and ketjen black. The total mass fraction of the conductive agent system is 5%-60%.

[0013] The copper foil current collector is a smooth-surfaced electrolytic copper foil or a rough-surfaced copper foil treated by roughening, and the thickness thereof is 5-20 μm. The thickness of the composite coating is 2-20 μm, and the area density thereof is 0.1-2.0 mg cm -2 .

[0014] The preparation method of the anode sheet comprises the following steps:

[0015] S1. Raw material preparation: micron-sized dendritic silicon powder with a three-dimensional dendritic porous structure is used as the active component, and the powder can be prepared by existing mature processes such as acid etching of silicon-aluminum alloy.

[0016] S2. The dendritic silicon powder and the conductive agent containing conductive carbon black are mixed in a predetermined mass ratio. The second binder (at least one of sodium alginate, sodium carboxymethyl cellulose, and polyacrylic acid) is dissolved or dispersed in deionized water to prepare an aqueous solution or dispersion with a concentration of 1-5 wt%. Then, the first binder (styrene-butadiene rubber emulsion) and the mixed dry powder of dendritic silicon and conductive agent are added to form a mixture. First, the solid powder is fully wetted and dispersed by pre-stirring at a rotation speed of 200-800 rpm at room temperature for 0.5-2 h; then, the rotation speed is increased to 800-2000 rpm for 2-12 h of continuous intensive stirring to homogenize the slurry; finally, the slurry is placed in an ultrasonic device for dispersion at an ultrasonic power of 100-800 W for 0.5-4 h to obtain a highly uniform and stable composite slurry.

[0017] S3. Coating and drying of the pole piece: the uniform slurry obtained in step S2 is coated on the surface of the copper foil current collector by means of blade coating or slot die coating at a coating rate of 5-30 mm s -1 . The wet pole piece after coating is first dried by blowing air at 50-70℃ for 1-4 h, and then transferred to a vacuum drying oven for drying at 80-100℃ under a vacuum degree of less than -0.08 MPa for 4-12 h. After drying, the pole piece is rolled to obtain the dendritic silicon-based composite negative pole piece.

[0018] In a second aspect, the present application provides a negative electrode-free lithium battery using the pole piece described above and an asymmetric electrochemical activation method thereof.

[0019] The negative electrode-free lithium battery comprises a positive electrode, an electrolyte, a separator, and the dendritic silicon-based composite negative pole piece as described in the first aspect.

[0020] The active material of the positive electrode can be selected from at least one of LiFePO4, LiNi x Co y Mn z O2, LiNi x Co y Al z O2, or a lithium-rich manganese-based material, preferably with an active material surface loading of 10-20 mg cm -2 .

[0021] The electrolyte is composed of a lithium salt dissolved in an organic solvent. The lithium salt can be selected from at least one of LiFSI and LiTFSI, with a concentration of 1.0-3.0 mol L -1The solvent can be selected from DME, DOL and mixtures thereof. Additives such as LiNO3, FEC, etc. can be added to the electrolyte, and the amount of addition is 0.5% to 5% of the total mass.

[0022] The separator is a polyolefin porous separator or a ceramic-coated separator, and the thickness is 10 to 25 μm. Preferably, the battery is operated in the electrochemical activation method as described below during the cycle.

[0023] The core of the asymmetric electrochemical activation method is that, in the battery charging and discharging cycle, an asymmetric current program with a constant current discharge rate greater than a constant current charging rate is applied. This program controls the kinetics so that the dendritic silicon always remains in an incomplete lithium extraction state (i.e., maintained as Li x Si alloy, 0 < x < 3.75), thereby forming and dynamically maintaining a stable interface layer rich in silicon-lithium alloy in the coating of the pole piece.

[0024] The mechanism of the alloy interface layer is twofold: on the one hand, the silicon-lithium alloy itself is an excellent lithiumophilic material that can provide a large number of low-energy barrier nucleation sites; on the other hand, its good ion / electron conductivity can effectively reduce the reduction resistance of lithium ions at the interface, thereby significantly reducing the nucleation overpotential and growth overpotential of lithium deposition. Both of them work together to fundamentally guide the uniform and dense deposition of lithium metal.

[0025] As a specific and preferred embodiment of the method, when the anode-free full battery uses LiFePO4 as the positive electrode material, the asymmetric current program can specifically include: first, 2 cycles of constant current charging and discharging activation at 0.1C rate (charging cutoff voltage 3.7 V to 4.0 V, discharging cutoff voltage 2.0 V to 2.8 V); then enter the main cycle stage, use 0.05C to 0.5C rate constant current charging to 3.7 V to 4.0 V, and use 0.3C to 3C rate constant current discharging to 2.0 V to 2.8 V. In this specific embodiment, the above asymmetric rate strategy ensures the incomplete lithium extraction state of the dendritic silicon.

[0026] It should be noted that, in order to separately verify the lithium deposition / stripping reversibility and structural stability of the dendritic silicon-based composite anode pole piece itself, a standard half-cell (with metal lithium as the counter electrode) can be used for symmetric cycle testing. This test is an effective means to evaluate the basic electrochemical performance of the pole piece, and its excellent cycle stability is a prerequisite for forming the dynamic interface layer in the full battery and achieving long-term cycling.

[0027] Compared with the prior art, the present application has the following beneficial effects:

[0028] (1) The micron-sized dendritic silicon composite coating is combined with an asymmetric electrochemical activation procedure of "small current charging - large current discharging", forming a complete set of method of material and process synergy, effectively solving the problem of dynamic failure of the interface of the anode-free battery which is difficult to deal with by single material modification or single process optimization.

[0029] (2) Through the above activation procedure, the dendritic silicon coating can be kept in an incomplete delithiation state during the cycle process, thereby forming and dynamically maintaining a stable interface layer rich in silicon-lithium alloy on the surface of the copper foil current collector in situ, ensuring the interface stability during long-term cycling.

[0030] (3) The dynamic interface layer can provide abundant lithiumophilic nucleation sites and significantly reduce the lithium deposition overpotential, thereby synergistically guiding uniform and dense lithium deposition, effectively inhibiting the generation of lithium dendrites and "dead lithium", and improving the cycle life and safety of the battery.

[0031] (4) The preparation process of the negative electrode sheet of the application is based on mature water-based coating technology, and the overall scheme is compatible with existing battery production lines, simple process, controllable cost, easy to scale production and application. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The SEM cross-sectional structure diagram of the dendritic silicon-based composite negative electrode sheet prepared in Example 1 of the application.

[0033] Figure 2 The cycle efficiency curve of Example 1 in the dendritic silicon-based half-cell (0.5 mA cm -2 Current density, 0.5 mAh cm -2 Cut-off capacity).

[0034] Figure 3 The charge specific capacity and coulombic efficiency curve of Example 2 in the dendritic silicon-based anode-free full cell (0.3C charging / 0.5C discharging) with the number of cycles.

[0035] Figure 4 The charge specific capacity and coulombic efficiency curve of Example 3 in the dendritic silicon-based anode-free full cell (0.3C charging / 2C discharging) with the number of cycles.

[0036] Figure 5 The charge specific capacity and coulombic efficiency curve of Example 4 in the dendritic silicon-based anode-free full cell (0.3C charging / 2C discharging) with the number of cycles.

[0037] Figure 6 The charge specific capacity and coulombic efficiency curve of Example 5 in the dendritic silicon-based anode-free full cell (0.3C charging / 2C discharging) with the number of cycles.

[0038] Figure 7 Coulombic efficiency of Comparative Example 1 (pure copper foil) in half-cell (0.5 mA cm -2 Current density, 0.5 mAh cm -2 Coulombic efficiency as a function of cycle number.

[0039] Figure 8 Charge specific capacity and Coulombic efficiency of Comparative Example 2 (pure copper foil) in full-cell without negative electrode (0.3C charge / 0.5C discharge) as a function of cycle number.

[0040] Figure 9 Charge specific capacity and Coulombic efficiency of Comparative Example 3 (pure copper foil) in full-cell without negative electrode (0.3C charge / 2C discharge) as a function of cycle number. DETAILED DESCRIPTION

[0041] In order to make the objects, technical solutions and advantages of the present application clearer, the specific embodiments of the present application will be described in detail below with reference to the drawings. The following examples are only used to illustrate the present application and are not considered as limiting the present application.

[0042] Example 1: Preparation of dendrite silicon-based composite negative electrode and performance test in half-cell

[0043] This example describes in detail the preparation of the dendrite silicon-based composite negative electrode and its basic electrochemical performance in a half-cell.

[0044] (1) Preparation of micron-sized dendrite silicon material: Take 10 g of silicon-aluminum alloy powder (Changsha Tianjiu Metal Material Co., Ltd., average particle size about 5 μm). Add it to 200 mL of 3 mol / L hydrochloric acid solution, and stir at room temperature with a magnetic stirrer at a speed of 300 rpm. Each cleaning lasts 1.5 h, and is repeated 3 times to completely remove the aluminum component. After acid washing, wash with deionized water until neutral. Then, immerse the obtained silicon material in 100 mL of 5% hydrofluoric acid solution at room temperature for 5 min to form a three-dimensional dendritic porous structure. Immediately after etching, wash with a large amount of deionized water until neutral, and finally dry in vacuum at 80°C for 6 h to obtain micron-sized dendrite silicon powder.

[0045] (2) Preparation of binder solution: Dissolve sodium alginate powder in deionized water to prepare a 2 wt% sodium alginate aqueous solution, which is ready for use. Butyl rubber is used in the form of a commercially available emulsion (solid content about 50%).

[0046] (3) Preparation of dendrite silicon-based composite negative electrode sheet: ingredients are prepared in a mass ratio of: dendrite silicon: butadiene rubber (calculated as solid): sodium alginate (calculated as solid): graphene: conductive carbon black = 60:2:18:10:10. The specific operation is as follows: 0.06 g of dendrite silicon, 0.01 g of graphene, and 0.01 g of conductive carbon black are weighed and mixed uniformly. 0.9 g of the above-mentioned 2 wt% sodium alginate aqueous solution is taken. The mixed dry powder is added to the sodium alginate aqueous solution, and first stirred at a speed of 500 rpm for 1 h for pre-mixing and wetting. Subsequently, 0.002 g of butadiene rubber emulsion is added, and the stirring speed is increased to 1500 rpm, and the strong stirring is continued for 6 h. Finally, the slurry is placed in an ultrasonic instrument for ultrasonic treatment at a power of 300 W for 2 h to obtain a uniform and stable composite slurry. The slurry is coated on a smooth electrolytic copper foil with a thickness of 8 μm using an automatic coating machine, and the wet film thickness is set to 10 μm. The coated electrode sheet is first dried at 60°C for 2 h, and then transferred to a vacuum drying oven for drying at 90°C under a vacuum degree lower than -0.08 MPa for 10 h. After rolling and cutting, a dendrite silicon-based composite negative electrode sheet with a diameter of 14 mm is obtained. The surface activity loading of the composite coating after drying is 0.24 mg cm -2 .

[0047] (4) Half-cell assembly: in an argon atmosphere glove box, the electrode sheet prepared in Example 1 is used as the working electrode, a lithium metal sheet is used as the counter electrode and reference electrode, a polypropylene separator is used, the electrolyte is a 1 M LiTFSI DME:DOL (volume ratio 1:1) solution, and 3 wt% LiNO3 is added as an additive. A CR2032 type button cell shell is used for packaging.

[0048] (5) Test procedure: the assembled half-cell is placed in a constant temperature environment for testing. The test procedure is as follows: at a current density of 0.5 mA cm -2 , constant current discharge for 1 h (lithium deposition, corresponding to a surface capacity of 0.5 mAh cm -2 ), and then constant current charging to 0.8 V (vs. Li + / Li) at the same current density, which is one cycle, and the long cycle test is carried out in this way.

[0049] Example 2: Anode-free full cell battery using the electrode sheet of Example 1 (0.3C charging / 0.5C discharging)

[0050] This example provides an anode-free lithium battery using the electrode sheet described in Example 1.

[0051] (1) Cell assembly: the positive electrode uses a commercially available LiFePO4 electrode sheet with an active material surface loading of 12.0 mg cm -2The negative electrode uses the electrode tab prepared in Example 1. The separator, electrolyte composition, and battery packaging environment are the same as in Example 1. A CR2025 type button cell shell is used for assembly.

[0052] (2) Test procedure: The charge-discharge test procedure of the battery is as follows: first, 2 cycles of constant current charge-discharge activation at 0.1C rate (based on the theoretical capacity of LiFeP04 170 mAh g -1 ) with a voltage range of 2.4 V to 3.8 V. After activation, enter the cycle stage: constant current charge to 3.8 V at 0.3C rate, then constant current discharge to 2.4 V at 0.5C rate.

[0053] Example 3: Anode-free full battery using the electrode tab of Example 1 (0.3C charge / 2C discharge)

[0054] This example provides another anode-free lithium battery using the electrode tab described in Example 1, which differs from Example 2 in that the charge-discharge rate of the cycle stage is different.

[0055] (1) Battery assembly: same as Example 2.

[0056] (2) Test procedure: The activation procedure is the same as in Example 2. After activation, enter the cycle stage: constant current charge to 3.8 V at 0.3C rate, then constant current discharge to 2.4 V at 2C rate.

[0057] Example 4: Preparation of a composite negative electrode tab with low silicon content and full battery test (0.3C charge / 2C discharge)

[0058] (1) Tab preparation: The preparation process is the same as in Example 1. The mass ratio is adjusted to: dendritic silicon: butadiene rubber (calculated as solid): sodium alginate (calculated as solid): graphene: conductive carbon black = 40:2:18:20:20.

[0059] (2) Battery assembly and testing: The full battery assembly method is the same as in Example 2. The test procedure is the same as in Example 3 (0.3C charge / 2C discharge).

[0060] Example 5: Preparation of a composite negative electrode tab with high silicon content and full battery test (0.3C charge / 2C discharge)

[0061] (1) Tab preparation: The preparation process is the same as in Example 1. The mass ratio is adjusted to: dendritic silicon: butadiene rubber (calculated as solid): sodium alginate (calculated as solid): graphene: conductive carbon black = 70:2:18:5:5.

[0062] (2) Battery assembly and testing: The full battery assembly method is the same as in Example 2. The test procedure is the same as in Example 3 (0.3C charge / 2C discharge).

[0063] Comparative Example 1: Pure copper foil negative half-cell

[0064] (1) Negative electrode tab: The same bare smooth copper foil as in Example 1 was used, with a thickness of 8 pm, cut into a 14 mm diameter disc.

[0065] (2) Half-cell assembly and testing: The assembly procedure, electrolyte composition, and testing procedure were all identical to Example 1, except that the working electrode was replaced with the pure copper foil described in this comparative example.

[0066] Comparative Example 2: Pure copper foil negative anode-free full cell (0.3C charge / 0.5C discharge)

[0067] (1) Negative electrode tab: The same pure copper foil as described in Comparative Example 1.

[0068] (2) Full cell assembly and testing: The assembly procedure, positive electrode used, electrolyte, separator, and testing procedure were all identical to Example 2, except that the negative electrode was replaced with the pure copper foil described in this comparative example.

[0069] Comparative Example 3: Pure copper foil negative anode-free full cell (0.3C charge / 2C discharge)

[0070] (1) Negative electrode tab: The same pure copper foil as described in Comparative Example 1.

[0071] (2) Full cell assembly and testing: The assembly procedure, positive electrode used, electrolyte, separator, and testing procedure were all identical to Example 3, except that the negative electrode was replaced with the pure copper foil described in this comparative example.

[0072] Test results and analysis

[0073] The above examples and comparative examples were tested, and the key performance data is summarized in the following table:

[0074] Table 1. Anode-free lithium battery cycle performance

[0075] In the half-cell test, as shown in the comparison of the coulombic efficiency curves of Figure 2 (Example 1) and Figure 7 (Comparative Example 1), the electrode with dendritic silicon composite coating exhibited extremely high cycle reversibility, with coulombic efficiency remaining high and stable (average > 99.5%) for more than 400 cycles; while the pure copper foil electrode showed significant efficiency decay after about 200 cycles. This confirms that the micron-sized dendritic silicon coating can provide abundant lithium-philic nucleation sites, effectively reduce the lithium deposition potential barrier, and buffer the volume change during deposition / detachment, thereby significantly improving the basic electrochemical stability of the negative electrode interface.

[0076] The synergistic effect of the application is systematically verified in the full-cell test without negative electrode. Under the low-rate asymmetric procedure of 0.3C charging / 0.5C discharging Figure 3 With Figure 8 , the capacity retention rate of Example 2 (63.5%) is obviously higher than that of Comparative Example 2 (48.1%) with pure copper foil. This indicates that even in the relatively small polarization degree asymmetric procedure, the pure program optimization is difficult to overcome the fundamental defect of the insufficient lithium affinity of the surface of the pure copper foil.

[0077] Under the high-rate asymmetric procedure of 0.3C charging / 2C discharging, the advantage of the synergy of the material and the procedure is more prominent. As shown in Figure 4 , Figure 5 , Figure 6 , Examples 3, 4 and 5 with different formulations (silicon content 40%~70%) all show effective cycle performance, and the capacity retention rate is between 70.0% and 76.0% after 100 cycles. In contrast, Comparative Example 3 with pure copper foil shows a sharp performance decline, and the capacity retention rate is only 1.2% ( Figure 9 ). This huge difference highlights the effectiveness of the core mechanism of the application: the asymmetric activation procedure controls the kinetics, so that the dendritic silicon remains in a partially lithiated state during the cycle, thereby forming and dynamically maintaining a stable interface layer rich in Li x Si alloy in situ in the coating. This interface layer continuously provides lithium-affine sites and reduces the deposition overpotential, thereby guiding uniform lithium deposition.

[0078] The above results collectively show that the core advantage of the application lies in the dynamic synergy of the micron-sized dendritic silicon composite coating and the specific asymmetric electrochemical procedure. The dendritic silicon coating provides the structural basis and lithium-affine sites, while the asymmetric procedure provides the kinetic guarantee for interface stability. The synergistic effect of the two can effectively inhibit the growth of lithium dendrites and the formation of "dead lithium" under different silicon contents and high polarization at high rates, thereby significantly improving the cycle life and safety of the full-cell without negative electrode, and successfully solving the technical problem of the disconnection between "static interface modification" and "isolated program regulation" in the background technology.

[0079] The above is only a specific implementation of the application, but the protection scope of the application is not limited thereto. Any changes or replacements that can be easily thought of by those skilled in the art within the technical scope disclosed by the application should be covered within the protection scope of the application.

Claims

1. A dendritic silicon-based composite negative electrode sheet for use in a negative electrodeless lithium battery, characterized in that, The present invention includes a copper foil current collector and a composite coating disposed on the surface of the copper foil current collector; the composite coating comprises an active component, a binder and a conductive agent; the active component is micron-sized dendritic silicon.

2. The dendritic silicon-based composite negative electrode according to claim 1, characterized in that, The micron-sized dendritic silicon has a three-dimensional dendritic structure and is porous, with a particle size D50 of 1~20 μm.

3. The dendritic silicon-based composite negative electrode according to claim 1, characterized in that, Based on the total mass of the composite coating, the mass percentage of the micron-sized dendritic silicon is 10% to 90%, the total mass percentage of the binder is 5% to 30%, and the total mass percentage of the conductive agent is 5% to 60%, and the sum of the mass percentages of the three is 100%.

4. The dendritic silicon-based composite negative electrode according to claim 3, characterized in that, The adhesive comprises a first adhesive and a second adhesive, wherein the first adhesive is styrene-butadiene rubber, and its mass percentage is 0.5% to 5%, and the second adhesive is selected from at least one of sodium alginate, sodium carboxymethyl cellulose, and polyacrylic acid; the conductive agent comprises a first conductive agent and a second conductive agent, wherein the first conductive agent is conductive carbon black, and its mass percentage is 2% to 20%, and the second conductive agent is selected from at least one of acetylene black, carbon nanotubes, graphene, and Ketjen black.

5. The dendritic silicon-based composite negative electrode sheet according to any one of claims 1 to 4, characterized in that, The copper foil current collector is a smooth copper foil or a porous copper foil, and the thickness of the smooth copper foil or the porous copper foil is 5 μm to 20 μm; the thickness of the composite coating is 2 μm to 20 μm, and the areal density is 0.1 to 2.0 mg / cm³. -2 .

6. An asymmetric activation method for a negative electrode-free lithium battery, characterized in that, Applicable to a lithium metal-free full cell comprising the dendritic silicon-based composite anode sheet according to any one of claims 1 to 5, the method comprising: during the charge-discharge cycle of the full cell, applying an asymmetric current program with a constant current discharge rate greater than the constant current charge rate, so that the micron-scale dendritic silicon remains in an incompletely de-lithiated state during the cycle, thereby forming and maintaining a lithiumophilic interface layer rich in Li x Si (0 < x < 3.75) alloy on the surface of the anode sheet.

7. The asymmetric activation method according to claim 6, characterized in that, The asymmetric current program is as follows: constant current charging is performed at a rate of 0.05C to 0.5C, and constant current discharging is performed at a rate of 0.3C to 3C.

8. A negative electrode-free lithium battery, characterized in that, It includes a positive electrode, an electrolyte, a separator, and a dendritic silicon-based composite negative electrode sheet as described in any one of claims 1 to 4.

9. A method for assembling and activating a negative electrode-free lithium battery, characterized in that, include: Provides a dendritic silicon-based composite negative electrode sheet as described in any one of claims 1 to 4; The electrode is assembled with the positive electrode, electrolyte, and separator to form a full battery. The activation method described in claim 6 or 7 is applied to the full battery.

10. An energy storage device, characterized in that, It includes the negative electrode-free lithium battery as described in claim 8 or the negative electrode-free lithium battery prepared by the method described in claim 9.

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