Advanced Sulfur-Silicon Full Cell Architecture for Lithium Ion Batteries

by:CTECHi     2019-12-07
Ion batteries are critical for future energy storage.
However, the current energy density of lithium
Ion batteries are not enough for future applications.
Sulfur cathode and silicon anode have received wide attention in this field due to their high capacity potential.
While the latest developments in sulfur and silicon electrodes show exciting results in the semi-battery format, when combining the two electrodes into a complete battery format, none of them can be used as lithium
The current method of adding lithium to sulfur
The Silicon full battery includes pre-lithium Silicon or the use of lithium sulfur.
However, these methods complicate the processing of materials and cause potential safety hazards.
Here, we propose a new all-battery architecture, bypassing the issues associated with the current approach.
This battery structure allows lithium to enter the external circuit, thus gradually integrating the controlled amount of pure lithium into the system.
Using this method, after 250 cycles under C/10, a 50wh/kg with high specific energy density was obtained.
This work will pave the way for future research on sulfur
Silicon full batteryLithium-ion batteries (LiBs)
Superior to other battery technologies on the market, making them the choice of consumer electronics and electric vehicles (EVs).
However, the demand for performance and cost has begun to exceed the capabilities of the current LiB technology.
In order to purchase cheaper and larger batteries, researchers turned to the next generation of battery materials.
Current LiBs use a cathode made of lithium metal oxides such as lithium nickel manganese cobalt oxide (NMC).
Traditionally, the cathode is offset by a graphite anode, although some in the industry have recently begun to incorporate silicon into the anode (1–5%).
The advantages of this combination are high speed rate capability, low capacity degradation and long life.
The disadvantage is that the energy density is limited, and the theoretical energy density of NMC/graphite under 605wh/kg is the highest, and the cost is as high as $180/kWh.
To reduce costs, researchers have turned to more energy density and cheaper materials.
The theoretical capacity of sulfur is 1675 mAh/g, which is an attractive cathode material.
However, due to the inherent problems of sulfur, including multi-sulfur shuttle, bulk expansion and poor conductivity, the implementation of sulfur has been slow.
Polysulfur shuttle is produced by high-order polysulfur compounds dissolved in the electrolyte, which can cause long-term capacity degradation and slow reaction dynamics during operation.
Volume expansion caused by sulfur expansion (80%)
In the process of lithium conversion/lithium removal, the mechanical degradation of the electrode conductive network will be caused.
Finally, the insulation performance of sulfur affects the rate capability of the electrode.
Fortunately, researchers have found ways to mitigate these problems, from mechanical barriers to porous carbon networks to other chemical methods.
These solutions have good performance and therefore have a great passion for sulfur.
The selected current anode is silicon because of its theoretical capacity up to 4200 mAh/g.
Silicon faces two challenges
Poor conductivity, expansion of volume.
During the lithium/de-lithium process, the volume of silicon changes by 400%, the electrode is mechanically crushed and its cycle life and rate capability are reduced.
To alleviate these problems, the researchers used new methods including nano-silicon structures, conductive additives and adhesives.
Ultimately, great attention to solving each electrode problem has led to less work in the study of binding sulfur cathode and silicon anode in a complete electrode
Cell configuration.
The full battery using sulfur and silicon electrodes is attractive for several reasons.
Sulfur and silicon are good and rich for the environment.
In addition, the theoretical energy density of all Silicon sulfurcell (SSFCs)
1982 Wh/kg, far exceeding the theoretical energy density of the current LiBs, and the potential cost is only $13/kWh.
However, a major limitation of SSFCs is the lithium source.
At present, researchers use
Lithium-based materials, such as lithium sulfur or lithium Silides, allow energy density up to 600wh/kg.
However, these complete cell cycles are short, usually less than 50 cycles, while the materials used require specialized equipment and face limitations during processing.
Here, we propose an advanced LiB architecture that uses the sulfur cathode and silicon anode to integrate the lithium source into the silicon anode, which can bypass these problems.
At C/10, SSFC exhibits the energy density of one cycle in 260 cycles.
As far as we know, SSFC with this architecture has not been reported yet.
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