CN110233282B - All-solid-state battery with silicon cathode and sulfide solid electrolyte - Google Patents

All-solid-state battery with silicon cathode and sulfide solid electrolyte Download PDF

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CN110233282B
CN110233282B CN201910534209.9A CN201910534209A CN110233282B CN 110233282 B CN110233282 B CN 110233282B CN 201910534209 A CN201910534209 A CN 201910534209A CN 110233282 B CN110233282 B CN 110233282B
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许晓雄
黄晓
吴林斌
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Zhejiang Funlithium New Energy Tech Co Ltd
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    • H—ELECTRICITY
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Abstract

The invention relates to a silicon cathode lithium ion battery, and discloses an all-solid-state battery with a silicon cathode and sulfide solid electrolyte, which comprises a battery core, wherein the battery core comprises a cathode, a solid electrolyte layer and an anode, the cathode comprises a current collector and a lithium embedding layer which is laminated and fixed on the side surface of the current collector, the lithium embedding layer is formed by pressing mixed powder comprising sulfide electrolyte powder and silicon cathode powder, the silicon content in the mixed powder is 40-53 wt%, the particle size of the sulfide electrolyte powder is 10-100 nm, the particle size of the silicon cathode powder is 10-100 nm, the porosity of the lithium embedding layer is 15-23%, the lithium embedding layer can self-adaptively adjust the expansion/contraction caused by the process of releasing and embedding lithium from the silicon cathode powder, reduce the possibility of cracking and pulverization of the lithium embedding layer, and ensure the stable electrical contact between the embedded desulfurization layer and the current collector and the solid electrolyte layer respectively, therefore, the capacity attenuation of the high-silicon cathode solid-state battery is slowed down, and the cycle performance of the high-silicon cathode solid-state battery is improved.

Description

All-solid-state battery with silicon cathode and sulfide solid electrolyte
Technical Field
The invention relates to a silicon cathode lithium ion battery, in particular to an all-solid-state battery with a silicon cathode and sulfide solid electrolyte.
Background
Silicon is the lithium ion battery negative electrode material with the highest specific capacity (4200mAh/g) discovered by human beings so far, the negative electrode capacity density of the silicon is ten times higher than that of graphite, and the silicon is the most potential negative electrode material, and in addition, the silicon also has the advantages of abundant natural reserves (the second abundant element in the earth crust), no harm to the environment, low electrochemical potential and the like.
However, the silicon is still not widely used as the negative electrode material of the lithium ion battery, and has a limitation on the commercial application. This limitation is due to the nature of silicon itself, which is largely divided into two aspects.
In a first aspect, where silicon is the negative electrode material for lithium ion, each silicon atom may carry about four lithium atoms. The lithium intercalation mechanism is such that Si is converted to Li upon intercalation4.4Si, volume expansion of about 440%. During the process of lithium intercalation/deintercalation of silicon,large volume expansion/contraction generates large stress change, silicon is cracked and crushed, the cathode material is degraded, the electrode material is separated from the current collector, and then electric contact is lost, so that capacity is rapidly attenuated, and cycle performance is deteriorated. In contrast, in the current technology, about 10 wt% of silicon is doped into a graphite negative electrode material, so that a silicon-carbon composite negative electrode material is constructed, and the volume expansion and contraction change of the negative electrode is slowed down. But the effect of a small amount of added silicon on the improvement of the energy density of the battery is limited, and compared with other cathode materials with advantages, the advantage of high specific volume of the silicon material is not fully developed, so that the commercial application significance of the silicon cathode battery is reduced.
Secondly, the conductivity distribution on the silicon surface is not uniform, if no treatment is carried out, the SEI film formed on the silicon surface is not uniform and has pores, and the electrolyte can always contact the surface soaked in the silicon, so that the SEI film is very thick, the lithium consumption of the lithium ion battery is large, and the performance of the whole battery is not good. In addition, the silicon active material is pulverized due to volume expansion/contraction, the specific surface area is increased, the electrolyte is consumed on the newly generated surface, and the SEI is generated through reaction until the electrolyte is consumed, so that the battery is invalid. In this regard, in the current technology, a liquid electrolyte is used in the silicon negative electrode battery, and the amount of the electrolyte needs to be excessive, but the excessive addition of the electrolyte not only reduces the energy density of the battery, but also has the effect of only delaying the failure time of the battery.
Therefore, the current silicon negative electrode battery is expected to be developed toward commercial application and further improvement of the cycle stability is required.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide an all-solid-state battery with a silicon cathode and a sulfide solid electrolyte, wherein the all-solid-state battery is prepared from the silicon cathode and the sulfide solid electrolyte in combination with the solid electrolyte, so that the cycle performance of the high-silicon cathode is improved, the specific capacity attenuation of the high-silicon cathode is slowed down, and the all-solid-state battery with good cycle performance and high capacity is obtained.
The technical purpose of the invention is realized by the following technical scheme:
the utility model provides an all solid-state battery with silicon negative pole and sulphide solid electrolyte, includes electric core, electric core includes negative pole, solid electrolyte layer and positive pole, the negative pole includes the mass flow body and is fixed in the lithium embedding layer of mass flow body side, the lithium embedding layer is pressed by the mixed powder including sulphide electrolyte powder grain, siliceous negative pole powder, conductive carbon and forms, silicon content is 40~53wt% in the mixed powder, the particle size of sulphide electrolyte powder grain is 10~100 nm, the granularity of siliceous negative pole powder is 10~100 nm, the porosity of lithium embedding layer is 15~ 23%.
By adopting the technical scheme, the sulfide electrolyte powder and the silicon-containing negative electrode powder are mixed together, pressed and shaped to obtain the lithium intercalation layer, wherein the sulfide electrolyte powder contributes to uniform high ionic conductivity, and the silicon-containing negative electrode powder contributes to high specific capacity.
The sulfide electrolyte powder particles have a certain deformation amount, and the elastic modulus of the sulfide electrolyte powder particles is obviously higher than that of the liquid electrolyte. When the silicon in the lithium intercalation layer expands in the lithium intercalation process, sulfide electrolyte powder particles embedded between the silicon-containing cathode powder bodies are compressed, so that the influence of expansion of the silicon-containing cathode powder bodies to increase the lithium intercalation layer and even the overall volume of the anode can be relieved.
And the lithium embedding layer is provided with 15-23% of porosity, when the silicon is embedded with lithium and expands, the porosity is reduced under compression, so that the porosity is sacrificed, a space for volume expansion is provided, and the increase of the whole volume of the positive electrode due to the lithium embedding layer and even the increase of the whole volume of the positive electrode is slowed down.
The porosity and the sulfide electrolyte powder particles have a synergistic effect, the original pores are also used for the sulfide electrolyte powder particles to deform under pressure, cracking caused by concentrated internal stress of a de-intercalation layer is avoided, and meanwhile, the surface deformation or cracking caused by silicon intercalation lithium expansion and the interface electric contact bonding performance between a negative electrode and a solid electrolyte are reduced in the prior art;
and then the sulfide electrolyte powder particles in the whole lithium intercalation layer are mutually abutted and pressed to form a framework frame, the framework frame is expanded after the whole lithium intercalation layer expands, inward contraction force exists on the lithium intercalation layer, the expansion limit of a de-intercalation layer is inhibited, the possibility of expansion and pulverization of the lithium intercalation layer is reduced, and when the silicon-containing negative electrode powder is de-lithiated and contracted, the contraction force of the framework frame assists the contraction and recovery of the lithium intercalation layer, so that the surface smoothness of the lithium intercalation layer subjected to the contraction and recovery is improved, and the electrical contact stability of the lithium intercalation layer with the solid electrolyte layer and a current collector is ensured.
In conclusion, the lithium intercalation layer can adaptively adjust the expansion/contraction caused by the process of lithium intercalation and deintercalation of the silicon-containing cathode powder, reduce the possibility of cracking and pulverization of the lithium intercalation layer, and ensure the stable electrical contact between the lithium intercalation layer and the current collector and between the lithium intercalation layer and the solid electrolyte layer, thereby slowing down the capacity attenuation of the high-silicon cathode solid-state battery and improving the cycle performance of the high-silicon cathode solid-state battery.
The invention is further configured to: the solid electrolyte layer is formed by pressing a solid electrolyte powder at the interface of the negative electrode side.
By adopting the technical scheme, the bonding tightness of the negative electrode and the solid electrolyte layer is improved, the electric contact stability is improved, and the interface impedance between the negative electrode and the solid electrolyte layer is reduced.
Meanwhile, the solid electrolyte layer can generate tensile expansion deformation when the lithium intercalation layer shrinks, the volume of the lithium intercalation layer is reduced to adapt, and the electric contact stability of the solid electrolyte layer and the lithium intercalation layer under long-term circulation is improved.
The invention is further configured to: the solid electrolyte powder is a sulfide solid electrolyte.
By adopting the technical scheme, the cathode contains the sulfide electrolyte, the solid electrolyte powder comprises the sulfide solid electrolyte, the sulfide solid electrolyte and the solid electrolyte have the same components, and when the solid electrolyte layer is pressed, the combination stability of the cathode and the solid electrolyte layer is higher, so that the interface impedance between the cathode and the solid electrolyte layer is reduced.
Meanwhile, the solid electrolyte layer can be easily compressed and deformed when the lithium intercalation layer expands, and the volume change of the lithium intercalation layer is adapted, so that the electric contact stability of the solid electrolyte layer and the lithium intercalation layer is improved.
The invention is further configured to: the positive electrode is obtained by pressing positive electrode material powder on an interface of the solid electrolyte layer on the side opposite to the negative electrode.
By adopting the technical scheme, the electric contact stability of the anode and the solid electrolyte layer in the application is improved, the interface impedance between the anode and the solid electrolyte layer is reduced, and when the solid electrolyte layer is jacked to the anode or is far away from the anode due to the volume change of the cathode, the anode can still be stably combined with the solid electrolyte layer.
The invention is further configured to: and after the negative electrode, the solid electrolyte layer and the positive electrode are combined to obtain the battery cell, the battery cell is clamped inwards from two sides of the positive electrode and the negative electrode, pressed and placed in an environment with the temperature of 200-300 ℃, and treated at high temperature for 5-10 min.
By adopting the technical scheme, because the cathode and the solid electrolyte layer both contain the same component, namely the solid electrolyte, the lithium intercalation layer and the interface attached to the solid electrolyte layer are fused under high-temperature treatment, and the contact impedance between active substances in the battery is reduced.
The invention is further configured to: the mixed powder also contains Li2S, Li in the lithium intercalation layer2The mass ratio of S to Si was 0.08: 1.
By adopting the technical scheme, Li2S plays a role in lithium supplement when an SEI film is formed on the surface of the silicon-containing negative electrode powder, so that the expansion of the SEI film formed by external lithium on the lithium intercalation layer and the expansion separation among internal particles are reduced, the tightness of the lithium intercalation layer is ensured, and the possibility of cracking of the lithium intercalation layer is reduced.
The invention is further configured to: the Li2S is uniformly dispersed or immobilized on the surface of the sulfide electrolyte powder particles.
By adopting the technical scheme, Li2S is not added independently as powder or granule, so as to avoid Li2The loss of S during the SEI film formation process causes a change in internal compactness and binding force of the lithium intercalation layer, and a reduction in deformation cracking resistance and battery cycle performance of the lithium intercalation layer.
The invention is further configured to: li in the mixed powder of the lithium intercalation layer2S point of dispersionThe reason is as follows:
weighing Li in proportion2S and sulfide solid electrolytes using Li2Organic solvent dispersed Li for S and sulfide solid electrolyte reaction2S and sulfide solid electrolyte, and the S and the sulfide solid electrolyte are uniformly mixed, sprayed, granulated and dried to obtain the electrolyte.
By adopting the technical scheme, Li2S is uniformly dispersed in sulfide electrolyte powder particles, so that an SEI film is formed uniformly.
In conclusion, the invention has the following beneficial effects:
1. the lithium intercalation layer can adaptively adjust the expansion/contraction caused by the process of releasing and intercalating the lithium from the silicon-containing cathode powder, reduce the possibility of cracking and pulverization of the lithium intercalation layer and ensure the stable electrical contact between the lithium intercalation layer and the current collector and the solid electrolyte layer respectively, thereby slowing down the capacity attenuation of the high-silicon cathode solid-state battery and improving the cycle performance of the high-silicon cathode solid-state battery.
2. The solid electrolyte layer is formed by pressing and fixing sulfide solid electrolyte powder on a negative electrode interface, so that the combination tightness of the negative electrode and the solid electrolyte layer is further improved, the electric contact stability is improved, the interface impedance between the negative electrode and the solid electrolyte layer is reduced, meanwhile, the solid electrolyte layer can be stretched, expanded and deformed when the lithium intercalation layer shrinks, the volume of the lithium intercalation layer is reduced to adapt, and the electric contact stability of the solid electrolyte layer and the lithium intercalation layer under long-term circulation is improved.
3. The positive pole is obtained by pressing and fixing the positive pole material powder on the side of the solid electrolyte layer back to the negative pole, so that the electric contact stability of the positive pole and the solid electrolyte layer in the application is improved, the interface impedance between the positive pole and the solid electrolyte layer is reduced, and when the solid electrolyte layer is pushed to the positive pole or is far away from the positive pole due to the volume change of the negative pole, the positive pole can still be stably combined with the solid electrolyte layer.
4.Li2S plays a role in lithium supplementation when an SEI film is formed on the surface of silicon-containing negative electrode powder, reduces the expansion of the SEI film formed by external lithium on the lithium intercalation layer and the expansion separation among internal particles, ensures the tightness of the lithium intercalation layer, reduces the possibility of cracking of the lithium intercalation layer, and simultaneously Li2S is not added independently as powder or granule, so as to avoid Li2The loss of S during the SEI film formation process causes a change in internal compactness and binding force of the lithium intercalation layer, and a reduction in deformation cracking resistance and battery cycle performance of the lithium intercalation layer.
Drawings
Fig. 1 is a cross-sectional view of an all-solid battery;
fig. 2 is a cross-sectional view showing the cell structure layering.
Reference numerals: 1. a housing; 2. an aluminum-plastic film; 3. an electric core; 31. a negative electrode; 311. a current collector; 312. embedding a lithium layer; 32. a solid electrolyte layer; 33. and (4) a positive electrode.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
In the case of the example 1, the following examples are given,
as shown in fig. 1, the all-solid-state battery with a silicon negative electrode and a sulfide solid electrolyte comprises a shell 1, an aluminum plastic film 2 and a battery core 3. The battery core 3 is wrapped by the aluminum plastic film 2 and then accommodated in the shell 1. The shapes of the aluminum plastic film 2 and the housing 1 can be determined according to the shape and size of the battery cell 3 in practical situations, which are not the creation point of the invention, and therefore, the detailed description is not provided herein.
As shown in fig. 2, the cell 3 includes a negative electrode 31, a solid electrolyte layer 32, and a positive electrode 33.
Negative electrode 31 includes a current collector 311 and a lithium insertion layer 312. The current collector 311 is a conductive material, and can be determined according to the actual design requirement, and is a copper foil with a thickness of 8 μm.
The lithium intercalation layer 312 has a thickness of 38 μm and a porosity of 20% and is obtained by pressure-pressing the mixed powder on one side of the current collector 311.
The mixed powder is formed by mixing silicon-containing cathode powder, sulfide electrolyte powder and an auxiliary agent.
The silicon-containing negative electrode powder is a nano-scale Si/C composite material, and the particle size is 50 nm.
The sulfide electrolyte powder is sulfide solid electrolyte, here Li2S-P2S5-LiI, particle size 50 nm.
The auxiliary material is Li2S powder particles, Li2The S powder particles are uniformly dispersed and distributed on the surfaces of the sulfide electrolyte powder particles. Li2The ratio of the particle size of the S particles to the particle size of the sulfide electrolyte, where Li is 1:52The S particle size is 10 nm.
The content of the components in the mixed powder is as follows, and the Si/C composite material comprises the following components: 75.76 wt%, Si: 53 wt%; li2The mass ratio of S to Si in the powder mixture is 0.08, where Li2S: 4.24 wt%; the proportion of the sulfide electrolyte powder particles in the mixed powder is 20 wt%.
The solid electrolyte layer 32 has a thickness of 70 μm and is obtained by pressure-pressing solid electrolyte powder particles on the side of the lithium intercalation layer 312 facing away from the current collector 311. The solid electrolyte powder particles used for the solid electrolyte layer 32 may be selected according to the actual conditions, and a sulfide solid electrolyte is preferred here, and is a composition Li of the same kind as the sulfide electrolyte powder particles in the mixed powder2S-P2S5LiI, particle size 2 μm.
The positive electrode 33 had a thickness of 65 μm and was obtained by press-fixing a positive electrode material powder on the side of the solid electrolyte layer 32 facing away from the negative electrode 31. The positive electrode material powder may be determined according to the actual situation, and here, the positive electrode material powder is LiNi0.8Co0.1Mn0.1O2(NCM811), sulfide solid electrolyte and conductive carbon material, wherein the compound proportion is that NCM 811: LGPS: conductive carbon 85:14: 1. Wherein the NCM811 particle size is 8 μm; the sulfide solid electrolyte is Li10GeP2S12(LGPS) particle size 2 μm; the conductive carbon is acetylene black with a particle size of 10 nm.
The production steps of the all-solid-state battery with the silicon negative electrode and the sulfide solid electrolyte of the present application are as follows.
S1: weighing Li in proportion2S and Li2S-P2S5LiI powder, using Li-free particles2S、Li2S-P2S5Organic solvent dispersed Li of LiI powder particle reaction2S and Li2S-P2S5LiI particles, where the organic solvent is chosen according to the actual situation, toluene, n-heptane etc., n-heptane being used here. Uniformly mixing, spraying, granulating and drying to obtain the watchSurface dispersed with Li2Li of S2S-P2S5-LiI powder particles. Then dispersing the obtained surface with Li2Li of S2S-P2S5Mixing the LiI powder particles with the Si/C composite material powder according to the proportion to obtain mixed powder.
S2: the mixed powder was spread on one side of the current collector 311, and the lithium intercalation layer 312 was isostatically pressed at a pressing pressure of 55MPa, to obtain the negative electrode 31.
S3: and spreading solid electrolyte powder particles on the side of the lithium embedding layer 312 opposite to the current collector 311, and carrying out isostatic pressing under the pressurizing pressure of 45MPa to obtain the solid electrolyte layer 32 with the integrated negative electrode 31.
S3: mix NCM811 in proportion: LGPS: and conducting carbon to obtain anode material powder, paving the anode material powder on the side of the solid electrolyte layer 32, which is opposite to the negative electrode 31, and performing isostatic pressing to form an anode 33, thus obtaining the battery core 3 pressed into a whole.
S4: and clamping the battery cell 3 from two sides of the anode 33 and the cathode 31, applying pressure which is vertical to the solid electrolyte layer 32, wherein the pressurizing pressure is 10MPa, and placing the battery cell at 260 ℃ for high-temperature treatment for 7-10 min.
S5: and (3) coating the cell treated in the step (S3) with an aluminum-plastic film 2, mounting parts such as tabs and the like, and mounting the shell 1 to obtain the all-solid-state battery. The electrode size was 5cm × 5cm, and the design capacity (calculated as the positive electrode) was 100 mAh.
Examples 2 to 4 are all-solid-state batteries with a silicon negative electrode and a sulfide solid electrolyte, and based on example 1, parameters are adjusted to obtain examples 2 to 5. The parameters of examples 1-5 are shown in Table I.
Figure GDA0003101766960000061
Comparative example 1, an all-solid-state battery of a silicon negative electrode, which is different from example 4 in the composition of the negative electrode, was obtained by mixing and pressing 60 wt% of Al-LLZO, 3wt% of LiTFSI, 2 wt% of conductive carbon, 5 wt% of Polymer (PAN), and 30 wt% of silicon powder, and had a negative electrode thickness of 38 μm. The solid electrolyte layer 32 and the positive electrode layer were pressed with this negative electrode, and an all-solid battery was obtained.
Comparative example 2, a liquid battery with a silicon negative electrode, which is different from example 4 in the composition of the silicon negative electrode, the silicon negative electrode is prepared by mixing silicon powder, graphite negative electrode material, conductive carbon black and sodium carboxymethyl cellulose in the mass ratio of 1: 7.7:0.3: 1 and mixing. The preparation method is as follows,
silicon powder with the granularity of 50nm, a graphite negative electrode material with the granularity of 8 mu m, conductive carbon black (acetylene black) with the granularity of 50nm and sodium carboxymethyl cellulose are mixed according to the mass ratio of 1: 7.7:0.3: 1, adding deionized water, uniformly mixing to obtain slurry, magnetically stirring the slurry for 8 hours, scraping the slurry to the surface of a copper foil, drying the copper foil in a vacuum drying oven at 100 ℃ for 8 hours, and cooling to obtain the silicon cathode. The thickness of the coating on the silicon negative electrode is 87 μm, and the porosity is 20%.
1mol/L LiPF is selected as the other6The mixed solution of ethylene carbonate and dimethyl carbonate with the volume ratio of 1:1 is electrolyte; selecting a PE film as a battery diaphragm; selecting the same surface with the capacity of 4mAh/cm2The NCM811 (supra) was used as a positive electrode, and a 5cm × 5cm rectangular battery was constructed by combination.
Comparative example 3, a liquid silicon carbon negative electrode battery, which is different from example 4 in the composition of the silicon negative electrode, the silicon negative electrode is composed of silicon powder, graphite negative electrode material, conductive carbon black and sodium carboxymethyl cellulose in the mass ratio of 2: 6.7:0.3: 1. The preparation method is as follows,
silicon powder with the granularity of 50nm, a graphite negative electrode material with the granularity of 8 mu m, conductive carbon black (acetylene black) with the granularity of 50nm and sodium carboxymethyl cellulose are mixed according to the mass ratio of 2: 6.7:0.3: 1, adding deionized water, uniformly mixing to obtain slurry, magnetically stirring the slurry for 8 hours, scraping the slurry to the surface of a copper foil, drying the copper foil in a vacuum drying oven at 100 ℃ for 8 hours, and cooling to obtain the silicon cathode. The thickness of the coating layer on the silicon negative electrode is 76 μm, and the porosity is 20%.
1mol/L LiPF is selected as the other6The mixed solution of ethylene carbonate and dimethyl carbonate with the volume ratio of 1:1 is electrolyte; selecting a PE film as a battery diaphragm; selecting the same surface with the capacity of 4mAh/cm2The NCM811 (supra) was used as a positive electrode, and a 5cm × 5cm rectangular battery was constructed by combination.
Comparative example 4, a liquid silicon carbon negative electrode battery, which is different from example 4 in the composition of the silicon negative electrode, is composed of silicon powder, graphite negative electrode material, conductive carbon black (acetylene black) and sodium carboxymethyl cellulose in the particle size ratio of 3: 5.7:0.3: 1.
The preparation method is as follows,
silicon powder with the granularity of 50nm, a graphite negative electrode material with the granularity of 8 mu m, conductive carbon black (acetylene black) with the granularity of 50nm and sodium carboxymethyl cellulose are mixed according to the mass ratio of 3: 5.7:0.3: 1, adding deionized water, uniformly mixing to obtain slurry, magnetically stirring the slurry for 8 hours, scraping the slurry to the surface of a copper foil, drying the copper foil in a vacuum drying oven at 100 ℃ for 8 hours, and cooling to obtain the silicon cathode. The thickness of the coating layer on the silicon negative electrode is 65 μm, and the porosity is 20%.
1mol/L LiPF is selected as the other6The mixed solution of ethylene carbonate and dimethyl carbonate with the volume ratio of 1:1 is electrolyte; selecting a PE film as a battery diaphragm; selecting the same surface with the capacity of 4mAh/cm2The NCM811 (supra) was used as a positive electrode, and a 5cm × 5cm rectangular battery was constructed by combination.
The all-solid-state batteries prepared in examples 1 to 5 were subjected to charge and discharge tests with a current of 5mA (0.05C) in the first cycle in a 60 ℃ incubator with charge and discharge cutoff voltages of 4.1V and 2.8V, respectively; subsequently, a playback test was performed at a current of 50mA (0.5C), and the test results are shown in Table two.
For the liquid silicon-carbon cathode battery obtained in the comparative example 1, the charging and discharging cut-off voltages are respectively 4.1V and 2.8V at 100 ℃ and room temperature, and the charging and discharging test is performed for the first circle at 5mA current (0.05C); subsequently, a playback test was performed at a current of 50mA (0.5C), and the test results are shown in Table two.
Under the conditions of 60 ℃ and room temperature, the charge-discharge cutoff voltages of the liquid silicon-carbon cathode batteries obtained in the comparative examples 2-4 are respectively 4.1V and 2.8V, and the charge-discharge test is carried out on the liquid silicon-carbon cathode batteries in the first circle by 5mA current (0.05C); subsequently, a playback test was performed at a current of 50mA (0.5C), and the test results are shown in Table two.
Second, table of the test results of all-solid-state batteries manufactured in examples 1 to 5 and comparative examples 1 to 3
Figure GDA0003101766960000081
In the prior art, the ionic conductivity of the oxide solid electrolyte is very low in the case of unsintered powder, and when the oxide solid electrolyte is used as the sulfide solid electrolyte in the negative electrode of the all-solid battery (comparative example 1), the coulombic effect of the obtained all-solid battery is almost zero (4.8 mAh).
In comparative example 1, the silicon cathode was prepared by mixing Al-LLZO 60 wt%, LiTFSI 3wt%, conductive carbon 2 wt%, Polymer (PAN)5 wt%, and silicon powder 30 wt%, and the ionic conductive network in the all-solid battery was constructed and operated at 100 ℃.
Comparing the results of comparative example 1 and examples 1 to 5 in the table above, it can be seen that the capacity and cycle performance of the all-solid-state battery of the present application are superior to those of comparative example 1.
Meanwhile, as can be seen from the above table, the batteries of comparative examples 2 to 4 based on the organic electrolyte have a sharp decline in battery performance at 60 ℃ due to poor stability of the electrolyte. When the silicon content in the silicon negative electrode exceeds 10 wt% under the condition of 25 ℃, the cycle performance of the silicon negative electrode is seriously attenuated.
The all-solid-state battery has large first-loop charging capacitance, and still has good capacitance retention rate after being cycled for many times under the condition of keeping high negative silicon content. Therefore, the lithium-embedded layer can adaptively adjust the expansion/contraction caused by the process of releasing and embedding lithium of the silicon-containing cathode powder, reduce the possibility of cracking and pulverization of the lithium-embedded layer and ensure the stable electrical contact between the embedded desulfurization layer and the current collector and the solid electrolyte layer respectively, thereby slowing down the capacity attenuation of the high-silicon cathode solid-state battery and improving the cycle performance of the high-silicon cathode solid-state battery.
In example 5, the silicon-containing anode material particles with the size of 100nm are used, the initial discharge capacity and the capacity storage rate of the silicon-containing anode material particles are obviously inferior to those of examples 1 to 4 using the silicon-containing anode material particles with the small size, and the size of the Si particles is preferably 50 to 100nm, and is further preferably 50 nm.
Example 2 very small amount of Li was used2S-cladding batteryThe electrolyte is used for supplementing lithium. Since lithium is not sufficiently replenished, the capacity retention rate is excellent, but the first discharge capacity is low.
Comparative example 5, an all-solid battery with a silicon negative electrode and a sulfide solid electrolyte, based on example 4, had a porosity of 5% in the lithium intercalation layer.
Comparative example 6, an all-solid battery with a silicon negative electrode and a sulfide solid electrolyte, based on example 4, the lithium intercalation layer had a porosity of 15%.
Comparative example 7, an all-solid battery with a silicon negative electrode and a sulfide solid electrolyte, based on example 4, had a porosity of 30% in the lithium intercalation layer.
The results of the tests of the all-solid-state batteries obtained in comparative examples 5 to 7 are shown in Table III.
TABLE III test results of all-solid-state batteries obtained in comparative examples 5 to 7,
Figure GDA0003101766960000091
Figure GDA0003101766960000101
Comparing the detection results of example 4 in the second table with the detection results of comparative examples 5 to 7 in the third table, when the porosity of the lithium intercalation layer is lower than 15%, the cycle performance improvement effect of the all-solid-state battery with the silicon negative electrode and the sulfide solid electrolyte is poor.
Meanwhile, when the porosity of the lithium-embedded layer is lower than 23%, the cycle performance improvement effect of the all-solid-state battery with the silicon cathode and the sulfide solid electrolyte is still good, and the cycle performance improvement is still remarkable. However, the initial capacitance is reduced due to the increase of the porosity, and in consideration of obtaining higher energy density and larger capacitance of the battery, the porosity of the lithium intercalation layer is preferably 15-23%.
In the case of the example 6, it is shown,
an all-solid-state battery with a silicon negative electrode and a sulfide solid electrolyte is based on example 4, and is characterized in that the positive electrode is formed by pressing positive electrode material powder in advance and then is attached to and assembled with a solid electrolyte layer.
In the case of the example 7, the following examples are given,
an all-solid-state battery with a silicon negative electrode and a sulfide solid electrolyte is characterized in that a solid electrolyte layer is formed by pre-pressing solid electrolyte powder and then is attached to the negative electrode for assembly on the basis of embodiment 4; meanwhile, the anode is formed by pressing anode material powder in advance, and then is attached and assembled with the solid electrolyte layer.
In the case of the example 8, the following examples are given,
based on example 4, the silicon-containing negative electrode powder is a mixture of silicon monoxide and conductive carbon.
Comparative example 8, an all-solid battery with a silicon negative electrode and a sulfide solid electrolyte, based on example 4, is distinguished in that step S4 is eliminated during the preparation and the cell is subjected to the next step without being subjected to a high-temperature treatment.
Comparative example 9, an all-solid-state battery with a silicon negative electrode and a sulfide solid electrolyte, based on example 4, is different in that when S1 is prepared as a mixed powder, Li is weighed in proportion2Directly granulating Li after S and sulfide electrolyte powder2And mixing the S and the sulfide electrolyte powder particles to obtain mixed powder for other steps.
The test results of the all-solid-state batteries prepared in examples 6 to 8 and comparative examples 8 to 9 are shown in table four.
TABLE IV test results of all-solid-state batteries obtained in examples 6 to 8 and comparative examples 8 to 9
Figure GDA0003101766960000102
Figure GDA0003101766960000111
Comparing example 4 in Table two with examples 6 to 7 in Table four, it can be seen that the initial discharge capacity and cycle performance of example 4 are better than those of examples 6 to 7, and the initial capacity and cycle performance of example 6 are better than those of example 7. Therefore, the electrolyte layer and the positive electrode are obtained by pressing powder and a semi-finished product of the battery cell in the previous step, the combination tightness of the negative electrode and the solid electrolyte layer and the combination tightness of the solid electrolyte layer and the positive electrode can be improved, the electric contact stability is improved, the interface impedance between the negative electrode and the solid electrolyte layer is reduced, meanwhile, the solid electrolyte layer can be stretched, expanded and deformed when the lithium intercalation layer shrinks, the volume of the lithium intercalation layer is reduced to adapt, and the electric contact stability of the solid electrolyte layer and the lithium intercalation layer under long-term circulation is improved.
Comparing example 4 in table two with example 8 in table four, it can be seen that the initial discharge capacity and cycle performance of example 4 are better than those of example 8. The surface conductivity of the Si/C composite material is uniformly distributed, the formed SEI film is uniform and thin, the expansion degree is small during lithium intercalation, and the sulfide powder particles and the porosity of a lithium intercalation layer are matched to realize better stability of high silicon content in a negative electrode, so that the all-solid-state battery has higher capacity upper limit.
Comparing example 4 in table two with comparative example 7 in table four, it can be seen that the initial discharge capacity and cycle performance of example 4 are better than those of comparative example 7. The high-temperature treatment in the application can improve the combination tightness of the cathode and the solid electrolyte layer and the combination tightness of the solid electrolyte layer and the anode, reduce the interface impedance, and improve the battery capacitance and the cycling stability.
Comparing example 4 in table two with comparative example 8 in table four, it can be seen that the initial discharge capacity and cycle performance of example 4 are better than those of comparative example 8. In this application Li2S is not added separately as powder or granules, to make Li2S is uniformly dispersed in sulfide electrolyte powder particles, so that an SEI film is conveniently and uniformly formed, and Li is prevented from being used2The loss of S during the SEI film formation process causes a change in internal compactness and binding force of the lithium intercalation layer, and a reduction in deformation cracking resistance and battery cycle performance of the lithium intercalation layer.
The present embodiment is only for explaining the present invention, and it is not limited to the present invention, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present invention.

Claims (6)

1. An all-solid-state battery with a silicon cathode and sulfide solid electrolyte comprises a battery cell (3), wherein the battery cell (3) comprises a cathode (31), a solid electrolyte layer (32) and an anode (33), and is characterized in that the cathode (31) comprises a current collector (311) and a lithium embedding layer (312) fixed on the side surface of the current collector (311), the lithium embedding layer (312) is formed by pressing mixed powder comprising sulfide electrolyte powder particles, silicon-containing cathode powder and conductive carbon, the silicon content in the mixed powder is 40-53 wt%, the particle size of the sulfide electrolyte powder particles is 10-100 nm, the particle size of the silicon-containing cathode powder is 10-100 nm, and the porosity of the lithium embedding layer (312) is 15-23%;
the mixed powder also contains Li2S, Li in the Li-inserted layer (312)2The mass ratio of S to Si is 0.08:1, and the Li2S is uniformly dispersed on the surface of the sulfide electrolyte powder particles.
2. The all-solid battery with a silicon negative electrode and a sulfide solid electrolyte according to claim 1, characterized in that the solid electrolyte layer (32) is formed by pressing a solid electrolyte powder at the interface on the negative electrode (31) side.
3. The all-solid battery with a silicon negative electrode and a sulfide solid electrolyte according to claim 2, wherein the solid electrolyte powder is a sulfide solid electrolyte.
4. An all-solid battery with a silicon negative electrode and a sulfide solid electrolyte according to claim 3, characterized in that the positive electrode (33) is obtained by pressing a powder of a positive electrode material at the interface of the solid electrolyte layer (32) on the side facing away from the negative electrode (31).
5. The all-solid-state battery with the silicon negative electrode and the sulfide solid electrolyte is characterized in that after the negative electrode (31), the solid electrolyte layer (32) and the positive electrode (33) are combined to obtain the battery core (3), the battery core (3) is clamped inwards from two sides of the positive electrode (33) and the negative electrode (31) and is placed in an environment with the temperature of 200-300 ℃ for 5-10 min.
6. The all-solid battery with silicon negative electrode and sulfide solid electrolyte as claimed in claim 1, wherein Li in the mixed powder of the lithium intercalation layer (312)2The S dispersion treatment is as follows:
weighing Li in proportion2S and sulfide solid electrolytes using Li2Organic solvent dispersed Li for S and sulfide solid electrolyte reaction2S and sulfide solid electrolyte, and the S and the sulfide solid electrolyte are uniformly mixed, sprayed, granulated and dried to obtain the electrolyte.
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