a highly reversible lithium metal anode - li ion battery cell

Due to the high theoretical capacity of lithium metal, it has great application prospect as anode material in rechargeable battery.
However, due to the electrolyte decomposition on the surface of the lithium-ion anode during the electrolytic cycle and the formation of shoot crystals, it does not meet the cycle life and safety requirements of the rechargeable battery.
Here, we propose a novel electrolyte system that is relatively stable for lithium metals and relieves shoot growth.
Design Method of the system, combined with simulation, model
The system is designed based on experiments and on-site analysis.
It is found that the reduction potential of the solvent, the size of the salt ions and the viscosity of the electrolyte are the key parameters that determine the growth rate of the shoot crystal.
The lithium metal anode in contact with the designed electrolyte exhibits significant cycling capacity (
More than 100 cycles)
Under the high area capacity of 12 mah CM-2. The DFT/basis-
Base Group/6-311 + G(d,p)
Horizontal and polarized continuum models (PCM)
A description of the solvent effect was implemented in the Gaussian 03 package.
The reduction potential is calculated based on the difference in the total energy of the reduced and neutral molecules, which is determined based on the following reduction reactions: the neutrals represent solvent molecules and electrons, respectively.
In order to determine whether the calculation method used is effective, we compare the calculation results obtained using different density calculation levels with the experimental results for different solvent molecules ().
The AIMD simulation was implemented in the simulation package of de novo computing in Vienna (VASP)code.
All calculations are based on the Perdew-Burke Ernzerhof generalized gradient approximation of density functional theory (PBE-GGA).
Projector enhancement wave method, a super unit containing molecules whose exact quantity depends on the molar mass and density of each molecule determined by the experiment, and uses a Li plate with 80 atoms.
In all calculations, a time step of 1 fs and a nasal thermostat of 300 k were used.
The interface can be defined (− Li)
The total energy of the Super Battery containing solvent molecules and Li metal plates, and (; bulk)
It is the total energy of bulk solvent molecules at 300 µk and 1 ps. (Li; bulk)
It is the total energy of bulk Li.
Statistical model of diffusion
Limited Aggregation (DLA)was used.
In this model, Li ions diffuse until they collide and then attach to whatever they impact.
To describe the two. dimension-
Like the cell we used, we used two-
Size DLA model with box size of 200 × 6000;
5000 particles were used.
The bottom line of the box represents an anode, I. e.
The diffusion of Li ions is captured online.
It is assumed that the average collision time of the Li ion is proportional to the number of grids passed through in each random diffusion step.
To describe the drift motion, a higher weight probability is set in the direction of the anode.
The Li symmetrical coin cell is designed to evaluate the effect of electrolyte on the growth of lithium-crystalline, as shown.
Two pieces of lithium foil (Diameter: 16mm;
Thickness: 500 μ m)
Used as an electrode.
Pet film (Diameter: 19mm;
Thickness: 100 μ m), with a 12-
The center has mm holes and polypropylene gaskets (Diameter: 19mm;
Thickness: 1mm), with a 1-
The mm hole in its center is used to separate the electrode and expose its control area to improve the repeatability of the short electrodecircuit time .
Finally, fill the electrolyte into the battery and install the spring, gasket and gasket.
Discharge of Li symmetric cells (
Peel the lithium from the surface of the negative lithium electrode, thus cleaning it in a chemical way)
The current density is 0.
05 u2005 mA CM 10 u2005 h for conditioning.
Then it was charged (
Deposit lithium on the negative electrode)at 1.
By the way of the battery, 0 cucma cm-Test System (TOSCAT-
3100, Dongyang system).
The viscosity and conductivity of various electrolyte are measured using a web (
Anton palmac 302)
There is also a conductivity meter (
Metrohm) 856 conductivity module
At 21 °c, respectively.
We conducted more than five experiments and got an error of less than 10%.
In order to directly observe and record the growth of lithium shoots using a microscope system (
Shaft Pro, micro support)
As shown in the figure, an observation unit is designed.
Two lithium foils were used for the positive and negative poles.
Lithium is deposited on the negative electrode at a current density of 5.
0 ma cm through a constant potential meter/galvanostat (
Analysis of 1480 Multistat and Zhangjiagang city).
During the lithium deposition, the microscope takes an image of the lithium crystal at a capacity of 1. 67u2005mAh cm;
As shown in the figure. PEO (
Molecular weight: 6 × 10, Sigma-Aldrich; )
Powder, salt LiTFSI (Wako Chemical), and nano-SiO (Sigma-
Aldrich, 10-20 nm, Sigma-Aldrich)
Dissolve in methanol and stir at room temperature for 24 hours.
The weight ratio of PEO/LiTFSI/SiO is 14. 7:5. 3:1.
In order to synthesize the polymer electrolyte, the formed slurry is poured on the Teflon disk for 24 hours to allow acetone to evaporate, and then dried at 80 °c within 24 hours in a vacuum oven.
Li symmetrical coin battery is assembled using liquid electrolyte (
1 litm LiTFSI in various solvents)
And polymer electrolyte.
The cell structure is as follows: Li (0. 5u2005mm thick)
Liquid electrolyte (100u2005μL)
Polymer Electrolyte (50u2005μm)/separator (Celgard® 3501)
Liquid electrolyte (100u2005μL)+ polymer/Li (0. 5u2005mm)
, Where we used an electrolyte of more than 200 μ l because of the dead volume of the stuffed coin cells and the need for additional electrolyte extrusion during assembly. The cycle-
Using a battery test system, a 4 ma h life measurement is performed for each discharge and charge step in the case of a current density of 3 ma cm (TOSCAT-
3100, Dongyang system).
We confirmed the repeatability of the experiment, in which there was almost no difference in the experimental results, and the experimental results showed between 17 and 24 cycles, in which the number of cycles exceeded 100 in repeated experiments.