[0028] The detailed description set forth below in connection with the
appended drawings is intended as a description of various embodiments of the
present invention and is not intended to represent the only embodiments in which
the present invention may be practiced. Each embodiment described in this
disclosure is provided merely as an example or illustration of the present invention,
and should not necessarily be construed as preferred or advantageous over other
embodiments. The detailed description includes specific details for the purpose of
providing a thorough understanding of the present invention. However, it will be
apparent to those skilled in the art that the present invention may be practiced
without these specific details.
[0029] As used in the description herein and throughout the claims that follow,
the meaning of “a,” “an,” and “the” includes plural reference unless the context
clearly dictates otherwise. Also, as used in the description herein, the meaning of
“in” includes “in” and “on” unless the context clearly dictates otherwise.
[0030] The terms “or” and “and/or” as used herein are to be interpreted as
inclusive or meaning any one or any combination. Therefore, “A, B or C” or “A, B
and/or C” mean “any of the following: A; B; C; A and B; A and C; B and C; A, B
and C.” An exception to this definition will occur only when a combination of
elements, functions, steps or acts are in some way inherently mutually exclusive.
[0031] The present invention relates to a hybrid electrolyte additive with
improved electrolyte properties in terms of electrochemical performance. A metal
organic framework (MOF) and Zeolite Imidazolium Framework (ZIF) where the
MOF does not have redox active centre, which is a non-transition metal centre. The
MOF and ZOF are covalently bonded. The MOF(s) and ZIF(s) are porous materials
made up of metal ions and organic linkers. These metal ions form a framework and
organic linkers connect the metal ions together. In covalently bonded MOF(s) and ZIF(s), the metal ions, organic linkers and even the framework are covalently
bonded to each other. These covalent bonds are stronger than the electrostatic
interactions in conventional MOF(s) and ZIF(s), making it more rigid and less
susceptible to degradation. The rigid structure of covalently bonded MOF(s) and
ZIF(s) makes them more open and accessible to ions, providing higher ionic
conductivity, which can improve the performance of lithium-ion batteries. In
addition, the covalent bonds in covalently bonded MOF(s) and ZIF(s) make them
more stable at high temperatures and in harsh environments. This makes them more
suitable for use in lithium-ion batteries that are subjected to these conditions.
[0032] Fig. 1 illustrates selectively modifying the surface of ZIF and MOF
with reactive species to engage the same in a covalent bond. According to an
embodiment, University of Oslo (UiO-66) which is a prototypical MOF may be
incorporated with –OH (hydroxyl) groups at the time of synthesis itself. The –OH
incorporated UiO-66 (UiO-66-OH) (210) may then be treated with (3-
Aminopropyl)triethoxysilane (APTES) to incorporate amino groups in the same.
These amino groups from UiO-66-OH (210) then form covalent bonds with
aldehyde group of ZIF-90 (110), and thus provide a covalently bonded ZIF-MOF
(COV- MOF/ZIF) additive (220).
[0033] It is illustrated that the ethoxy groups of APTES reacts with surface
hydroxyl groups of the UiO-66-OH (210). The UiO-66-OH (210) is thus coated
with a white silanizated APTES layer. The APTES functionalized UiO-66-OH
(210) is then immersed into a Teflon liner, the amino groups reacts with the
aldehyde groups of imidazolate-2-carboxyaldehyde via imine condensation, and
then the nucleation and crystal growth of the ZIF-90 (110) starts at these fixed sites
on the surface of the UiO-66-OH (210). After solvothermal reaction, the APTES
modified silica fibber is completely coated with a uniform and dense ZIF-90 (110)
layer with a thickness of about 20 mm. The result strongly indicates that the
covalent linker between the ZIF-90 (110) and the UiO-66-OH (210) substrate
indeed promotes the formation of a compact ZIF-90 (110) layer on the APTES
modified substrate of UiO-66-OH (210).
embodiment, ZIF-90 (110) in the covalently bonded MOF/ZIF (220) helps in
trapping the smaller molecules such as H2O, CO2, HF and the like that cause
electrolyte degradation. Thus, improving cyclic stability of the electrochemical cell,
as shown in the Fig. 2. The MOF in the COV-MOF/ZIF helps in the formation of
robust inorganic SEI. In the combination of Zr-O-C and LiF, SEI reinforcement and
dendrite inhibition is achieved. The solid electrolyte interface (SEI) contribution
from Zr-MOF UiO-66-OH (210) leads to inclusion of compounds like LiF and ZrO-C which are les resistive and chemically stable. Also, the SEI contributed by
COV-MOF/ZIF is uniformly distributed and controlled.
[0037] Such COV-MOF/ZIF creates new mesoporous at the interface. It also
introduces various functional groups. A covalent bonding also increases the
electrolyte permeability, such that the porous additives in the electrolyte can
enhance its permeability by providing a network of interconnected pores. These
pores create pathways for ion diffusion and electrolyte flow, allowing for faster and
more uniform distribution of ions within the cell. Improved electrolyte permeability
leads to reduced concentration polarization and lower internal resistance, thus
improving the cell performance.
[0038] These porous additives are the reservoirs for the electrolyte solvent,
helping in retaining a higher electrolyte volume within the cell. The systems with
active material expansion or contraction during charge/discharge cycles gain
advantage due to the presence of porous additives which ensure a continuous supply
of solvent to compensate for volume changes, and thus maintaining good contact
between the electrolyte and electrode surface. This prevents the drying out of
electrolyte. The porous structure also facilitates ion transport by providing
additional pathways for ion movement within the electrolyte. The interconnected
pores create channels through which ions migrate, thus these reduce the diffusion
distances and promote faster ion mobility. This provides an improved rate of charge
transfer at the electrode-electrolyte interface. The porous structure can absorb or
trap unwanted reaction by-products, such as lithium dendrites or other metal
deposition, reducing the risk of electrode damage or short circuits. This helps to
maintain a stable and safe operating environment for the cell, preventing issues like
capacity loss, cell degradation, or thermal runaway.
[0039] The covalent bonds are stronger and more reliable than the noncovalent bonds, such as hydrogen bonding or van der Waals forces (typically
present in these material). The COV-MOF/ZIF also introduces functional groups
which enhances stability between the functional group and framework, making the
framework more robust and less prone to degradation or structural changes during
the electrochemical processes.
[0040] The functional groups are capable of modifying the pore size, shape,
and surface chemistry of the framework, allowing for precise control over ion
transport, diffusion, and adsorption within the framework. This controlled pore
environment may enhance the selectivity and efficiency of ion transport, leading to
improved electrochemical performance. The presence of these groups may
modulate the redox properties, charge transfer kinetics, or capacitive behaviour of
the materials. The functional groups may also modify electrochemical properties of
the frameworks to match the requirements of specific electrochemical systems,
leading to enhanced performance. These functional groups are capable of
facilitating redox reactions, enhance the kinetics of charge transfer reactions, or
promote the decomposition of undesired by-products in the electrolyte. The presence
of catalytic functional groups is also able to improve the overall efficiency, stability,
and reaction rates of the electrochemical system.
[0041] The covalent functional groups may also be designed to preferentially
adsorb or separate specific ions from the electrolyte solution. This selectivity is
useful in applications such as ion sieving, ion capture, or ion separation, allowing
for improved electrolyte purity or targeted ion transport. It also amplifies the
inherent properties of the frameworks. This also leads to enhanced stability, ion
transport, redox capacity, catalytic activity, thus the functionalized MOF(s) and
ZIF(s) are appropriate as additives. These covalent bonds ensures that the
compounds retains its structure and properties during electrochemical processes.
This also leads to reduced chances of particle aggregation or framework
degradation, thereby providing better dispersion and retention of the compound within the electrolyte, providing consistent performance. The covalent bonding
within the compound enables optimized ion transport pathways, thereby enabling
reduced ion tapping, enhancing the overall ionic conductivity and facilitating faster
ion transport within the electrolyte. The incorporation of specific functional groups,
pore sizes, or redox-active centers in the compound allows for precise control over
electrochemical properties, resulting in improved performance as an electrolyte
additive.
[0042] According to a preferred embodiment, a wet chemical method is
incorporated for the synthesis of the covalently bonded MOF and ZIF along with
the surface activation of the ZIF. The ZIF-90 (110) in an embodiment may be
synthesized by a water–alcohol-based method. Summarizing the process, 371.25
mg of zinc nitrate hexahydrate and 4.0 mg of Cetyltrimethylammonium bromide
(CTAB) were dissolved in the mixture of 20 mL H2O/tert-butanol (1: 1, v/v) as a
triggered solvent. Then, 480.0 mg of ICA and 50.0 mg of PVP may be dissolved in
the mixture of 20 mL H2O/tert-butanol (1: 1, v/v) as a modifier. After that, the
triggered solvent may be poured into the modifier and continuously stirred for 5
minutes at room temperature. Finally, a pale-yellow precipitate is formed. The ZIF90 (110) solid product is obtained by centrifugation (at 13,000 rpm for 10 minutes),
washed with excess ethanol, and vacuum-dried at 60 C for 12 h.
[0043] In another form of an embodiment, the synthesis of UiO-66-OH (210)Z
Zr-based MOF may be based on the method suggested by Katz et al, which basically
is done by using a 30 mL vial, ZrCl4 (125 mg, 0.54 mmol), 5 mL dimethyl
formamide (DMF) and 1 mL of concentrated HCL loaded and sonicated for 10 min
until all solids are fully dissolved. Then, 2 hydroxy terephthalic acid (135 mg, 0.75
mmol) and 10 mL DMF are added to the solution and sonicated for more than 20
minutes. The obtained mixture is then placed in an oven and heated at 80 °C for 12
hours. After cooling down to room temperature, the resulting solid is filtered,
repeatedly washed several times with DMF and then with ethanol. Finally, it is dried
at 120 °C under vacuum to give the MOF.
[0044] In view of the present disclosure which describes the present invention,
all changes, modifications and variations within the meaning and range of
equivalency are considered within the scope and spirit of the invention. It is to be
understood that the aspects and embodiment of the disclosure described above may
be used in any combination with each other. Several of the aspects and embodiment
may be combined together to form a further embodiment of the disclosure.
1. An electrochemical battery comprising;
a positive electrode;
a negative electrode;
an electrolyte;
said electrolyte comprises a Metal Organic framework (MOF) with
at least one hydroxyl group and at least one amino group and a Zeolite
Imidazolium Framework (ZIF) with at least one aldehyde group,
wherein the MOF and ZIF are covalently bonded to form an
electrolyte additive (220) for the said electrochemical battery.
2. The electrochemical battery as claimed in claim 1, wherein said MOF may
include at least one of UiO-66 and said ZIF may include at least one of ZIF90 (110).
3. The electrochemical battery as claimed in claim 1, wherein the MOF and
the ZIF incorporate reactive functional groups.
4. A method of preparing an electrolyte additive, comprising the steps of:
incorporating a hydroxyl (-OH) group into a Metal Organic
Framework (MOF) during synthesis;
treating said MOF with (3-Aminopropyl)triethoxysilane (APTES)
incorporating amino groups therein;
functionalizing Zeolite Imidazolium Framework (ZIF) to include
aldehyde groups therein;
forming covalent bonds between said amino groups of said MOF
and aldehyde groups of said ZIF creating a covalently bonded MOF/ZIF
electrolyte additive (220).
5. The method as claimed in claim 4, wherein the MOF and the ZIF incorporate
reactive functional groups.
6. The method as claimed in claim 4, wherein the said additive (220) is capable
of being modified at least on one of pore size, shape, surface function and
framework