Gel polymer electrolytes preparation

Kim, D.W. and Sun, Y.K. (2001) Electrochemical characterization of gel polymer electrolytes prepared with porous membranes. J. Power Sources. 

Lee KM, Hsu CY, Chiu WH, Tsui MC, Tung YL, Tsai SY, Ho KC (2009) Dye-sensitized solar cells with a micro-porous Ti02 electrode and gel polymer electrolytes prepared by in situ cross-link reaction. Sol Energy Mater Sol Cells 93(ll) 2003-2007... 

A gel polymer electrolyte prepared using P(AN-GMA [glycidyl methacrylate]) as the matrix and cross-linking with a-amino polypropylene oxide has an ionic conductivity of 8.23 x 10 S/cm at 25°C and good mechanical performance. 

Kim, J.K., Ahn, J.H., Jacobsson, P. 2014. Influence of temperature on ionic liquid-based gel polymer electrolyte prepared by electrospun fibrous membrane. Electrochim. Acta 116 321-325. 

Jiang J, Gao D, Li Z, Su G (2006) Gel polymer electrolytes prepared by in situ polymerization of vinyl monomers in room-temperature ionic liquids. React Funct Polym 66(10) 1141-1148.doi 10.1016/j. reactfunctpolym.2006.02.004... 

Ion exchangers are polymer electrolytes prepared a priori as insoluble solids (salts, acids, bases hydrated, possibly gel-Uke). Their polymer backbone is three-dimensional. Many are polyvinyl compounds (substituted polyethylenes) having the general formula [-CH2-CXH-] , where different substituents X lead to rather different products ... 

Multisubsituted linear polyphosphazene polymers, (II), having high ion conductivity at ambient temperature were prepared by Allcock [3] and used as gel polymer electrolytes. 

The addition of gel-forming components (plasticizers) to polymer electrolytes (see the above) produces gel like structures. Therefore, this type of ion-conducting polymers can also be described as gel polymer electrolytes. Gel polymer electrolytes can also be prepared, if a solution of a salt in an organic solvent is added to a polymer matrix (polyvinyl chloride, polyvinyl fluoride). The solvent dissolves in the polymer matrix and forms a gel like structure. The conductivity as well as the current density and rate of diffusion, etc., are determined by the mobUity of the solvated ions in the polymer matrix. The transport constants are again proportional to the free volume in the polymer. 

Jo et al prepared and characterised Gel polymer electrolytes composed of methy methacrylete-styrene copolymers (PMS) and electrolyte solution (LiT-FSI in EC/DMQ. Depending on the molar composition of the copolymer, these gel polymer electrolytes exhibited different electrochemical and mechanical properties. In order to investigate the physical interactions among organic solvents, polymer, and lithium ions occurred in the gel polymer electrolyte, Raman spectroscopy and solid state Li NMR spin-spin relaxation measurements were performed. 

Raghavan P, Manuel J, Zhao X, Kim D-S, Ahn J-H, Nah C (2011) Preparation and electrochemical characterization of gel polymer electrolyte based on electrospun polyacrylonitrile nonwoven membranes for lithium batteries. J Power Sources 196(16) 6742-6749. doi 10.1016/j.jpowsour.2010.10.089... 

A single-ion conductor containing a PEO unit can also be prepared for gel polymer electrolytes. For example, the lithium salt prepared as shown in Figure 11.3 is plasticized with EC or PC solvent, though the LP-ion transference number decreases with the amount of solvent added. When the number of EO units is greater than three, it behaves as a single-ion conductor and follows the VTF equation. The ionic conductivity remains relatively constant with varying numbers of EO units. 

PEO, followed by addition of the organic electrolyte (a mixture of EC/1,2-dimethoxyl methane (DME) plasticizer with 12 wt% LiCFgSOg). Its ionic conductivity is comparable with that of the organic electrolyte, 2 x 10 S/ cm. When LiA102 powder is added, the ionic conductivity of the prepared gel pol5mier electrolyte is about l(h S/cm, and its Lh-ion transference number (fy) is 0.2-0.4 with a decomposition voltage of 5.0 V. It is stable with Li metal since its passivation resistance stabilizes very quickly, which is different from other gel polymer electrolytes. 

Several ofher cross-linking methods can be applied. For example, acrylonitrile, methyl methacrylate (MMA), and its EO derivatives can be copolymerized and then cross-linked with diisocyanate. A thin gel membrane can be prepared by soaking a polyolefin nonwoven fabric in a solution of reactant(s), which is fhen cross-linked by means of ultraviolet radiation. The thickness of fhis fhin gel membrane is 50-100 pm, and the ionic conductivity is 2-4 X 10 3 S/cm. Compared to the gel polymer electrolyte made from dry PAN, fhis process is much simpler, and the energy consumption is 10% lower. However, there are also disadvantages. For example, imreacted monomer and residual catalyst are difficult to remove from the gel polymer electrolyte, leading to reduced ionic conductivity and stability of the polymer. To overcome these disadvantages, the acrylonitrile monomer is first polymerized in nonaqueous electrolyte, and then the unreacted monomer is removed by vacuum. Finally, a multifunctional monomer is added, and the battery is filled with the mixed solution. It is solidified by heating to get the gel polymer electrolyte. 

PMMA-based gel polymer electrolytes can be prepared by adding plasticizers in the polymer. Alternatively, they can be obtained by polymerization of the mixture of monomer, initiator, and plasticizers. 

A gel polymer electrolyte has been prepared by mixing a high-molecular-weight PMMA with clay followed by adding plasticizer (1 M LiC104 solution in EC/PC). The polymer matrix is embedded between the clay layers, leading to an increase in Tg. The solvent can permeate into the clay and does not separate from the clay in this gel polymer electrolyte. The ionic conductivity increases with an increasing amount of clay, up to a clay content of... 

Besides the common plasticizers mentioned in Table 11.2, borate can also be used as a plasticizer. After copolymerization of the two PEG methacrylate (PEG-M) monomers shown in Figure 11.18, a PEG borate ester (PEG-BE) or its mixture with PC is added. As the results show in Figure 11.19, the ionic conductivity of the prepared cross-linked gel polymer electrolyte is highest with the PEG-BE-PC mixture and is consistent with the Arrhenius equation. Its thermal and electrochemical stability and mechanical performance are good, and it has excellent cycling performance from room temperature to 65 C [14]. 

A P(BMA-St) copolymer has been prepared by reacting butyl methacrylate (BMA) and St monomers, followed by addition of 10 wt% fumed silica. The obtained gel polymer electrolyte has good thermal stability up to 355°C, and its pores are small and are evenly distributed. The voltage obtained with this gel polymer is 5.2 V (vs. Li+/Li). The ionic conductivity is 2.15 x 10 3 S/cm at room temperature. 

When PVDF is copolymerized, the crystallinity of the copolymer decreases, and the uptake of electrolytes increases. However, the melting point and the mechanical strength decrease. To make up for these deficiencies, a trifluoro-ethylene (TrFE) unit can be introduced to increase the melting point of the copolymer and the ratio of the amorphous domain. The prepared gel polymer electrolyte provides good electrochemical performance. 

When a microfiber network is introduced into the macroporous PVDF matrix, an interpenetrating network structure is obtained, and the prepared gel polymer electrolyte is stable during the charging and discharging processes [23]. 

The copolymer PAMS (AN-MMA-St) prepared by emulsion polymerization can be dissolved in organic electrolyte by heating and then coated on both sides of a PE microporous membrane. After cooling and solidification by cross-linking, the gel polymer electrolyte that is obtained shows an ionic... 

The matrices of polymers such as poly(vinyl pyrrolidone) (PVP), polysul-fone, poly(trimethylene carbonate) (PTMC), triethylene glycol diacetate-butyl propenoate copolymer [28], and cellulose [29] are different from the mentioned polymers in Sections from 11.1 to 11.5. For example, when porous polysulfone is used as the polymer carrier, the ionic conductivity (3.93 x 10 S/cm at room temperature) and mechanical performance are greatly improved after adding plasticizers. When organic electrolyte is added to PTMC, the uptake ability is greatly improved because its structure is similar to that of the organic electrolyte. Methylcellulose (MC) is prepared easily as a porous polymer membrane, as illustrated in Figure 11.34. It can absorb liquid electrolyte to become a gel polymer electrolyte whose ionic conductivity is 0.2 mS/cm and lithium-ion transference number is 0.29. These results can compare with the commercial separator [29]. 

Two modifications of plasticizers are generally applied. One is to use materials that have similar structures with the plasticizers mentioned in Table 11.1. As shown in Figure 11.35, phosphate can be used as a spacer to separate EO units. The other modification uses ionic liquids as plasticizers. Inorganic plasticizers are prepared by replacing the organic plasticizers in the gel polymer electrolyte with ionic liquids. For example, in the case of P(TFE-HFP) copolymer, it is mixed with an ionic liquid. The ionic conductivity at room temperature exceeds 10 S/cm, and rises to more than 10 S/cm at 100°C. As discussed in Section 9.7, the preparation of ionic liquid is simple. 

O.2UCIO4 is added with a small amount of polymer such as PPO and lithimn poly(lithium vinyl sulfonate), an ionic rubber that can transfer ions is obtained, with an ionic conductivity of 1(T S/cm at room temperature. However, the electrochemical window of the prepared ionic liquid currently is limited to about 3.5 V. As a result, the applications for the obtained gel polymer electrolyte are also limited and cannot meet the demands of high-voltage Uthiiun-ion batteries. 

Fan, H.H., Li, H.X., Fan, L.Z., Shi, Q. 2014. Preparation and electrochemical properties of gel polymer electrolytes using triethylene glycol diacetate-2-propenoic acid butyl ester copolymer for high energy density lithium ion batteries. 

In the early 1980s, Sony Corporation initiated research on polymer lithium-ion batteries. At that time there was no such term as "polymer lithium-ion battery." The main idea is to use a block copolymer of poly vinylidenefluoride-hexafluoro propylene (P(VDF-HFP) as a gel carrier for the organic electrolytes. The composition of this polymer lithium-ion battery is shown in Figure 14.7 [3]. Later, Samsung Corporation coated a polymer on the traditional separators to act as a host for the organic electrolytes to prepare gel polymer electrolytes. Sanyo Corporation added precursors of PEO and plasticizers (organic... 

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