The bulk of the scientific literature on Li-conducting solid (solvent-free) polymer electrolytes (SPEs) for applications such as Li-based batteries is focused on polyether-based materials, not least the archetypal poly(ethylene oxide) (PEO). A significant number of alternative polymer hosts have, however, been explored over the years, encompassing materials such as polycarbonates, polyesters, polynitriles, polyalcohols and polyamines. These display fundamentally different properties to those of polyethers, and might therefore be able to resolve the key issues restricting SPEs from realizing their full potential, for example in terms of ionic conductivity, chemical or electrochemical stability and temperature sensitivity. It is further interesting that many of these polymer materials complex Li-ions less strongly than PEO and facilitate ion transport through different mechanisms than polyethers, which is likely critical for true advancement in the area. In this review, >30 years of research on these 'alternative' Li-ion-conducting SPE host materials are summarized and discussed in the perspective of their potential application in electrochemical devices, with a clear focus on Li batteries. Key challenges and strategies forward and beyond the current PEO-based paradigm are highlighted.

Electrolytes comprising poly(ethylene carbonate) (PEC)/poly(trimethylene carbonate) (PTM C) with lithium bis(trifluoromethane sulfonyl)imide (LiTFSI) are prepared by a simple solvent casting method. Although PEC and PTMC have similar chemical structures, they are immiscible and two glass transitions are present in the differential scanning calorimetry (DSC) measurements. Interestingly, these two polymers change to miscible blends with the addition of LiTFSI, and the ionic conductivity increases with increasing lithium salt concentration. The optimum composition of the blend electrolyte is achieved at PEC6PTMC4, with a conductivity as high as 10(-6) S cm(-1) at 50 degrees C. This value is greater than that for single PEC- and PTMC-based electrolytes. Moreover, the thermal stability of the blend-based electrolytes is improved as compared to PEC-based electrolytes. It is clear that the interaction between C=O groups and Li+ gives rise to a compatible amorphous phase of PEC and PTMC.

Alternative solid polymer electrolytes (SPEs) hosts to the archetype poly(ethylene oxide) are gaining attention thanks to their appealing properties, such as higher cation transport number, thermal stability and electrochemical stability [1]. In addition, high mechanical stability is required in order to integrate easy-to-use materials into flexible or ‘structural’ batteries [2, 3].

 In this work, a solid polymer electrolyte (SPE) featuring high ionic conductivity and mechanical robustness at room temperature is presented. The SPE consists of a di-block copolymer, poly(benzyl methacrylate)-poly(ε-caprolactone-r-trimethylene carbonate) (BCT), mixed with different loadings of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The highest ionic conductivity achieved for these SPEs was found with 16.7 wt% LiTFSI loading (BCT17), reaching 9.1 x 10^-6 S cm^-1 at 30 °C. The limited current fraction (F₊) for the BCT17 electrolyte was calculated to be 0.64 with the Bruce-Vincent method. Furthermore, dynamic mechanical analysis showed a storage modulus (E’) of 0.2 GPa below 40 °C and 1 MPa above 50 °C. These results indicate that BCT with LiTFSI is a competitive electrolyte, combining high ionic conductivity and modulus at ambient temperatures.

 LiFePO₄|BCT17|Li half-cells showed good cycling performance at 60 °C. At 30 °C, where the SPE possessed significantly higher modulus, decent cell performance could still be achieved after several optimization steps. These included incorporating a SPE as binder, and infiltration cast the SPE on the electrode to maximize the contact between both components, thereby improving the interfacial contact and decreasing the cell resistance and overpotential when cycling the battery device.

 References

[1] J. Mindemark, M.J. Lacey, T. Bowden, D. Brandell. Prog Polym Sci, (2018). DOI: 10.1016/j.progpolymsci.2017.12.004.

[2] J.F. Snyder, R.H. Carter, E.D. Wetzel. Chem Mater, 19 (2007) 3793-801.

[3] W.S. Young, W.F. Kuan, Thomas H. Epps. J Polym Sci, Part B: Polym Phys, 52 (2014) 1-16.

A triblock copolymer of benzyl methacrylate and oligo(ethylene glycol) methyl ether methacrylate was polymerized to form the general structure PBnMA-POEGMA-PBnMA, using atom transfer radical polymerization (ATRP). The block copolymer (BCP) was blended with lithium bis(trifluoro methylsulfonate) (LiTFSI) to form solid polymer electrolytes (SPEs). AC impedance spectroscopy was used to study the ionic conductivity of the SPE series in the temperature interval 30 °C to 90 °C. Small-angle X-ray scattering (SAXS) was used to study the morphology of the electrolytes in the temperature interval 30 °C to 150 °C. By using benzyl methacrylate as a mechanical block it was possible to tune the microphase separation by the addition of LiTFSI, as proven by SAXS. By doing so the ionic conductivity increased to values higher than ones measured on a methyl methacrylate triblock copolymer-based electrolyte in the mixed state, which was investigated in an earlier paper by our group. A Li|SPE|LiFePO₄ half-cell was constructed and cycled at 60 °C. The cell produced a discharge capacity of about 100 mAh g⁻¹ of LiFePO₄ at C/10, and the half-cell cycled for more than 140 cycles.

In this work, three types of polymers based on epsilon-caprolactone have been synthesized: poly(epsilon-caprolactone), polystyrene-poly(epsilon-caprolactone), and polystyrene-poly(epsilon-caprolactone-r-trimethylene carbonate) (SCT), where the polystyrene block was introduced to improve the electrochemical and mechanical performance of the material. Solid polymer electrolytes (SPEs) were produced by blending the polymers with 10-40 wt% lithium bis(trifluoromethane) sulfonimide (LiTFSI). Battery devices were thereafter constructed to evaluate the cycling performance. The best performing battery half-cell utilized an SPE consisting of SCT and 17 wt% LiTFSI as both binder and electrolyte; a Li vertical bar SPE vertical bar LiFePO4 cell that cycled at 40 degrees C gave a discharge capacity of about 140 mA h g(-1) at C/5 for 100 cycles, which was superior to the other investigated electrolytes. Dynamic mechanical analysis (DMA) showed that the storage modulus E' was about 5 MPa for this electrolyte.

We report here a water-based functional binder framework for the lithium-sulfur battery systems, based on the general combination of a polyether and an amide-containing polymer. These binders are applied to positive electrodes optimised towards high-energy electrochemical performance based only on commercially available materials. Electrodes with up to 4 mAhcm(-2) capacity and 97-98% coulombic efficiency are achievable in electrodes with a 65% total sulfur content and a poly(ethylene oxide): poly(vinylpyrrolidone) (PEO: PVP) binder system. Exchange of either binder component for a different polymer with similar functionality preserves the high capacity and coulombic efficiency. The improvement in coulombic efficiency from the inclusion of the coordinating amide group was also observed in electrodes where pyrrolidone moieties were covalently grafted to the carbon black, indicating the role of this functionality in facilitating polysulfide adsorption to the electrode surface. The mechanical properties of the electrodes appear not to significantly influence sulfur utilisation or coulombic efficiency in the short term but rather determine retention of these properties over extended cycling. These results demonstrate the robustness of this very straightforward approach, as well as the considerable scope for designing binder materials with targeted properties.

A series of deuterated tri-block copolymers with the general structure d(8)-PMMA-POEGMA-d(8)-PMMA, with variation in d(8)-PMMA chain length, were synthesized using sequential controlled radical polymerization (ATRP). Solid polymer electrolytes (SPEs) were produced by blending tri-block copolymers and lithium bis(trifluoro methylsulfonate) (LiTFSI). Small-angle neutron scattering (SANS) was used to study the bulk morphology of the deuterated tri-block copolymer electrolyte series at 25 degrees C, 60 degrees C and 95 degrees C. The lack of a second T-g in DSC analysis together with modelling with the random phase approximation model (RPA) confirmed that the electrolytes are in the mixed state, with negative Flory-Huggins interaction parameters. AC impedance spectroscopy was used to study the ionic conductivity of the SPE series in the temperature interval 30 degrees C-90 degrees C, and a battery device was constructed to evaluate a 25 wt% d(8)-PMMA electrolyte. The Li | SPE | LiFePO4 cell cycled at 60 degrees C, giving a discharge capacity of 120 mAh g(-1), while cyclic voltammetry showed that the SPE was stable at 60 degrees C.

Background: Intraperitoneal adhesions cause significant morbidity. They occur after peritoneal trauma, which induces oxidative stress with production of inflammatory cytokines, peroxidized proteins (carbonyls) and lipids (aldehydes). This study aimed to investigate if carbazate-activated polyvinyl alcohol (PVAC), an aldehyde-carbonyl inhibitor, can reduce intraperitoneal adhesions in an experimental model.

Material and methods: Male Sprague-Dawley rats (n = 110) underwent laparotomy, cecal abrasion and construction of a small bowel anastomosis. They either were treated with intraperitoneal instillation of PVAC or were sutured with PVAC-impregnated sutures. Thromboelastography analysis was performed using human blood and PVAC. The lipid peroxidation product malondialdehyde (MDA) and inflammatory cytokines IL-1 beta and IL-6 were quantified in peritoneal fluid. At day 7, bursting pressure of the anastomosis was measured and adhesions were blindly scored.

Results: PVAC in human blood decreased the production of the fibrin-thrombocyte mesh without affecting the coagulation cascade. MDA, IL-1 beta and IL-6 were increased after 6 h without significant difference between the groups. PVAC-impregnated sutures reduced intraperitoneal adhesions compared to controls (p = 0.0406) while intraperitoneal instillation of PVAC had no effect. Anastomotic bursting pressure was unchanged.

Conclusions: Intervention with an aldehyde-carbonyl inhibitor locally in the wound by PVAC-impregnated sutures might be a new strategy to reduce intraperitoneal adhesions.

In the present work, a photopolymerized urethane-based poly(ethylene glycol) hydrogel is applied as a porous scaffold material using indirect solid freeform fabrication (SFF). This approach combines the benefits of SFF with a large freedom in material selection and applicable concentration ranges. A sacrificial 3D poly(epsilon-caprolactone) structure is generated using fused deposition modeling and used as template to produce hydrogel scaffolds. By changing the template plotting parameters, the scaffold channel sizes vary from 280 to 360 m, and the strut diameters from 340 to 400 m. This enables the production of scaffolds with tunable mechanical properties, characterized by an average hardness ranging from 9 to 43 N and from 1 to 6 N for dry and hydrated scaffolds, respectively. Experiments using mouse calvaria preosteoblasts indicate that a gelatin methacrylamide coating of the scaffolds results in an increased cell adhesion and proliferation with improved cell morphology.