184
6 Nanomaterials for Batteries
use of 3D porous copper mesh current collector/metal lithium composite negative
electrode can increase the cycle life, Coulombic efficiency and specific capacity
of batteries, which provide new ideas for the research of lithium metal negative
electrodes.
Stable Body Minimizes Volume Changes
The infinite volume expansion of lithium metal during deposition is also a serious
problem that hinders the development of lithium metal negative electrodes. Compared
to the volume expansion of 400% for silicon negative electrodes and 10% for graphite
negative electrodes, the volume expansion of lithium metal is more severe and almost
infinite, which causes the electrolyte/separator interface to float, generates internal
stresses, and accelerates cell damage. The CUI team developed a series of composite
lithium negative electrodes with a stable body to minimize the volume change of
the lithium metal negative electrode, including silicon-coated carbon nanofibers,
layered reduced graphene oxide, and zinc oxide coated carbon nanowires fiber (Lin
et al. 2016; Liu et al. 2016; Liang et al. 2016). Besides, the surface area of the
lithium negative electrode can also be increased, the effective current density can
be reduced, and the lithium-ion current can be uniformized, thereby inhibiting the
growth of lithium dendrite. The existence of a stable body can also decrease the
internal stress of the battery and increase the safety performance and cycle stability
of the battery.
6.5.6 Electrolyte Solution
6.5.6.1 Liquid Electrolyte
According to current literature reports, organic liquid electrolyte for the lithiumsulfur battery, the main electrolyte system includes two major categories of carbonate
solvent system.
Carbonate Solvent System
This type of system is mostly used for polymer sulfur composites such as PAN
and sulfur compounded by high temperature heat treatment (Wang et al. 2003,
2002), or use in microporous carbon–sulfur composites. Carbonate-based organic
solvents have low solubility in polysulfide ions. Therefore, as the reaction progresses
in a general carbon–sulfur composite system, the contact resistance between the
discharge product and the conductive agent increases. Only when the sulfur and the
composite materials are in a combined state or sulfur is in the form of small molecules
can the efficient transport of ions and electrons in the electrode be satisfied, and
carbonate organic solvents can work better. Under these conditions, the system has
low solubility of polysulfide ions, resulting in excellent cycle performance.
6 Nanomaterials for Batteries
use of 3D porous copper mesh current collector/metal lithium composite negative
electrode can increase the cycle life, Coulombic efficiency and specific capacity
of batteries, which provide new ideas for the research of lithium metal negative
electrodes.
Stable Body Minimizes Volume Changes
The infinite volume expansion of lithium metal during deposition is also a serious
problem that hinders the development of lithium metal negative electrodes. Compared
to the volume expansion of 400% for silicon negative electrodes and 10% for graphite
negative electrodes, the volume expansion of lithium metal is more severe and almost
infinite, which causes the electrolyte/separator interface to float, generates internal
stresses, and accelerates cell damage. The CUI team developed a series of composite
lithium negative electrodes with a stable body to minimize the volume change of
the lithium metal negative electrode, including silicon-coated carbon nanofibers,
layered reduced graphene oxide, and zinc oxide coated carbon nanowires fiber (Lin
et al. 2016; Liu et al. 2016; Liang et al. 2016). Besides, the surface area of the
lithium negative electrode can also be increased, the effective current density can
be reduced, and the lithium-ion current can be uniformized, thereby inhibiting the
growth of lithium dendrite. The existence of a stable body can also decrease the
internal stress of the battery and increase the safety performance and cycle stability
of the battery.
6.5.6 Electrolyte Solution
6.5.6.1 Liquid Electrolyte
According to current literature reports, organic liquid electrolyte for the lithiumsulfur battery, the main electrolyte system includes two major categories of carbonate
solvent system.
Carbonate Solvent System
This type of system is mostly used for polymer sulfur composites such as PAN
and sulfur compounded by high temperature heat treatment (Wang et al. 2003,
2002), or use in microporous carbon–sulfur composites. Carbonate-based organic
solvents have low solubility in polysulfide ions. Therefore, as the reaction progresses
in a general carbon–sulfur composite system, the contact resistance between the
discharge product and the conductive agent increases. Only when the sulfur and the
composite materials are in a combined state or sulfur is in the form of small molecules
can the efficient transport of ions and electrons in the electrode be satisfied, and
carbonate organic solvents can work better. Under these conditions, the system has
low solubility of polysulfide ions, resulting in excellent cycle performance.