This invention relates to a method of High-performance Si based anode for electrochemical battery.
BACKGROUND OF THE INVENTION
CN108028421B provides a silicon anode for a lithium ion battery, which includes a mixed binder in a mixing ratio of 10 wt.% to 90 wt.%. The combination of hybrid binders in Si anodes for rechargeable lithium ion batteries showed unexpected results, including extended cycle life and a balanced effect between adhesion strength and first cycle efficiency.
Research Gap: The reported capacity falls short to the expected capacity as presented.
Uniformity in the structure of the reported anode material is unfavourable for prolong cycling compared to the presented work.
EP3031092A1 discloses a Li-ion battery in one embodiment includes a lithium-based compound in a cathode, a first porous silicon portion in an anode, and a layer of atomic layer deposited (ALD) alumina coating the first porous silicon portion and contacting the cathode.
Research Gap: The reported work does not completely resolve the pulverization effect as compared to the presented.
US20120129054A1 dislcoses a silicon anode battery comprises: a housing; a battery core comprising a cathode, a silicon anode, and a separator disposed between the cathode and the silicon anode; and an electrolyte comprising at least one lithium salt, a non-aqueous solvent, and an additive, wherein the additive comprises diallyl pyrocarbonate.
Research Gap: Interfacial layer between electrode/electrolyte can diminish the capacity in the reported work as compared to the present.
• Pulverization effect still prevails in the reported work compared to the present work.
SUMMARY OF THE INVENTION
Promising electrode materials like Si and graphite when used as anode in electrochemical battery suffers greatly in charge storage capability with increased charge discharge cycles. This is due to pulverization resulting in inflation thereby hampering its crystal structure for charge storage capabilities. The electrodes of electrochemical battery suffer from inadequate surface activity resulting in an interfacial layer between electrode and electrolyte surface. This tends to deviate the charged particles coming towards the electrode thereby reducing its charge storage capability. Most of the promising anode materials like Si struggles in attracting charges due to their moderate conductivity. Development of a highly feasible technique to synthesize highly reliable electrode material at nanoscale dimension on commercialized purpose is still not achievable.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1: Flow chart for synthesis of Ag/MnO2/Si nanocomposite
DETAILED DESCRIPTION OF THE INVENTION
The presented invention tries to meet the growing demands of a sustainable energy resource. The dependency on fossil fuels are proved costly and the dust from burning of these fuels has been a major concern for clean environment. Moreover, the limiting capacity of the fossil fuels has already alarmed the world to find an alternative energy resource. Electrochemical batteries especially Li-ion battery has been used an alternative, however, its decaying capacity over prolonged charging and discharging has restricted its applications. Currently, Si is the most studied anode material to be used in electrochemical battery due for its high theoretical capacity of 4200 mAh/g, which is several times higher than the existing graphite material. Unfortunately, its use is restricted on large scale mostly due to pulverization effect by which the material gets inflated in shape under continuous charge discharge process. Here, a novel redox reaction method is utilized to make composite with Si with the use of MnO2 and Ag nanomaterials. MnO2 nanomaterial in 1D shape can hold fine Si nanoparticles. Moreover, the use of MnO2 nanomaterial can bond the Si nanoparticles in such a way to reduce its pulverization effect. The conductivity factor related to the anode can also be increased with the addition of an extra conducting and stable nanomaterial like Ag nanoparticles. Moreover, the nanoscale materials can offer high surface activity favourable for attracting more charges for high storage capability. The detailed procedures to develop such highly functional Ag/MnO2/Si anode material is presented with the help of the flowchart shown in Figure 1.
Synthesis of Si nanostructures: Cost effective silica sol of 4.4 g is reduced with 3 g magnesium by preparing a 40 ml solution and treating hydrothermally at 180 °C for 12 h. Further the precipitate collected is washed thoroughly with dilute HCl and HF to remove unwanted impurities to obtain highly pure Si nanostructures.
Synthesis of 1D MnO2: The redox reaction between Potassium permanganate (KMnO4) and Sodium nitrite (NaNO2) at 2:3 M is adjusted with the help of drop-wise addition of dilute H2SO4 solution followed by hydrothermal treatment at 170°C, 12 h. After the normal cooling, the precipitate is collected and washed thoroughly for several times with absolute ethanol. Finally, the precipitate is calcined to obtain 1D MnO2.
Synthesis of Ag nanoparticles: It is prepared by reducing silver nitrate (AgNO3) using sodium alginate (NaAlg). For this a clear solution of 40 ml containing 0.8 g NaAlg is prepared under moderate heating and continuous stirring. Then 0.04 M 1 ml AgNO3 is added into it, drop wise while maintain the reaction temperature close to 80 °C. Finally, the prepared solution is exposed to hydrothermal treatment at 150 °C for 12 h to obtain silver nanoparticles.
Synthesis of Ag/MnO2/Si nanocomposite anode: Adequate amounts of separately prepared Si nanostructures and Ag nanoparticles is added into a solution containing known amount of as prepared 1D MnO2 and vigorously stirred for half an hour. The as prepared solution is then transferred to autoclave for hydrothermal treatment at 150 °C for 12 h to obtain the nanocomposite. In a similar approach, other nanocomposites of Ag/MnO2, Si/Ag and Si/MnO2 is prepared following the hydrothermal method for a comparative analysis.
Testing of Anode in Li-ion battery: Normal coin cell is fabricated to test the charge storage capability of the anode material. Anode material is prepared by mixing as prepared materials with adequate amounts of conducting carbon black and suitable binder (PVDF). The as prepared electrode is coated over copper foil after making slurry using NMP. Li methal foil was used as cathode with 1.0 M LiPF6 in ethylene carbonate (EC) –diethyl carbonate (DEC) as electrolytes. Galvanostatic charge/discharge measurements is done at different current densities in a voltage range of 0.01 to 3.0 V vs Li/Li+ at ambient condition. Cyclic voltammogram (CV) is recorded with electrochemical workstation in the potential range of 0.01–3.0 V vs Li/Li+ at various scan rates (0.1 - 2 mVs-1) at ambient condition. Electrochemical impendence spectrum (EIS) is also measured with the same electrochemical workstation in a frequency range of 10 kHz – 10 MHz. A high anodic capacity close to 2000 mAh/g after 1000 cycles at 0.1 C-rate is achieved which can be further enhanced with the improved device fabrication technology.
Novel features of the Invention:
1. The proposed synthesis method can develop fine nanomcoposite at feasible condition.
2. The conductivity of the material can be enhanced with addition of stable nanomaterials like Ag.
3. The nanocomposite can rectify the shortcomings of other elemental compositions by a favourable bondings.
4. A stable anodic capacity can be claimed from the as prepared nanocomposite to be utilized in high performing electrochemical batteries.
ADVANTAGES OF THE INVENTION:
1. A reliable electrochemical energy storage device especially Li-Ion battery can be made with promisingly high anodic capacity.
2. Pulverization or instability in physical structure of Si anode can be controlled with the synergistic effect from MnO2 and Ag in the nanocomposite.
3. The invention will promote the technique to develop nanocomposite at commercialized scale.
4. The fine nanocomposite prepared can further be utilized in various other scientific domains such as Nano sensors, quantum electronic devices and nanobiotechnology.

We claim:

1. A method of High-performance Si based anode for electrochemical battery comprising the steps of: Synthesising of Si nanostructures; Synthesising of 1D MnO2 ; Synthesis of Ag nanoparticles, Synthesis of Ag/MnO2/Si nanocomposite anode; and Testing of Anode in Li-ion battery.
2. The method as claimed in claim 1, wherein silica sol of 4.4 g is reduced with 3 g magnesium by preparing a 40 ml solution and treating hydrothermally at 180 °C for 12 h; further the precipitate collected is washed thoroughly with dilute HCl and HF to remove unwanted impurities to obtain highly pure Si nanostructures.
3. The method as claimed in claim 1, wherein the redox reaction between Potassium permanganate (KMnO4) and Sodium nitrite (NaNO2) at 2:3 M is adjusted with the help of drop-wise addition of dilute H2SO4 solution followed by hydrothermal treatment at 170°C, 12 h; after the normal cooling, the precipitate is collected and washed thoroughly for several times with absolute ethanol; finally, the precipitate is calcined to obtain 1D MnO2.
4. The method as claimed in claim 1, wherein Synthesis of Ag nanoparticles is prepared by reducing silver nitrate (AgNO3) using sodium alginate (NaAlg); a clear solution of 40 ml containing 0.8 g NaAlg is prepared under moderate heating and continuous stirring; then 0.04 M 1 ml AgNO3 is added into it, drop wise while maintain the reaction temperature close to 80 °C; and the prepared solution is exposed to hydrothermal treatment at 150 °C for 12 h to obtain silver nanoparticles.
5. The method as claimed in claim 1, wherein separately prepared Si nanostructures and Ag nanoparticles is added into a solution containing known amount of as prepared 1D MnO2 and vigorously stirred for half an hour; and as prepared solution is then transferred to autoclave for hydrothermal treatment at 150 °C for 12 h to obtain the nanocomposite; and other nanocomposites of Ag/MnO2, Si/Ag and Si/MnO2 is prepared following the hydrothermal method for a comparative analysis.
6. The method as claimed in claim 1, wherein for Testing of Anode in Li-ion battery; normal coin cell is fabricated to test the charge storage capability of the anode material.
7. The method as claimed in claim 1, wherein anode material is prepared by mixing as prepared materials with adequate amounts of conducting carbon black and suitable binder (PVDF); and the as prepared electrode is coated over copper foil after making slurry using NMP. Li methal foil is used as cathode with 1.0 M LiPF6 in ethylene carbonate (EC) –diethyl carbonate (DEC) as electrolytes.
8. The method as claimed in claim 1, wherein Galvanostatic charge/discharge measurements is done at different current densities in a voltage range of 0.01 to 3.0 V vs Li/Li+ at ambient condition; and Cyclic voltammogram (CV) is recorded with electrochemical workstation in the potential range of 0.01–3.0 V vs Li/Li+ at various scan rates (0.1 - 2 mVs-1) at ambient condition.
9. The method as claimed in claim 1, wherein electrochemical impendence spectrum (EIS) is also measured with the same electrochemical workstation in a frequency range of 10 kHz – 10 MHz; and a high anodic capacity close to 2000 mAh/g after 1000 cycles at 0.1 C-rate is achieved which is further enhanced with the improved device fabrication technology.