Recent advances in solid-state lithium batteries based on anode engineering

Since limited energy density and intrinsic safety issues of commercial lithium-ion batteries (LIBs), solid-state batteries (SSBs) are promising candidates for next-generation energy storage systems. However, their practical applications are restricted by interfacial issues and kinetic problems, which result in energy density decay and safety failure. This review discusses the formation mechanisms of these issues from the perspective of typical solid-state electrolytes (SSEs) and provides an overview of recent advanced anode engineering for SSBs based on representative anodes including Li metal, graphite-based, and Si-based anodes, summarizing the advantages and problems of each strategy. The development of the anode-free batteries concept is demonstrated as well. Finally, recommendations are proposed for the potential directions in future research in anode engineering for SSBs

Synthesis of Sequence-Regulated Polymers: Alternating Polyacetylene through Regioselective Anionic Polymerization of Butadiene Derivatives

We hereby report a strategy to synthesize sequence-regulated substituted polyacetylenes using living anionic polymerization of designed monomers, that is, 2,4-disubstituted butadienes. It is found that proper substituents, such as 2-isopropyl-4-phenyl, lead to nearly 100% 1,4-addition during the polymerization, thus, giving product with high regioregularity, precise molecular weight, and narrow molecular weight distribution. The product is convertible into sequence-regulated substituted polyacetylene by oxidative dehydrogenation using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). Block copolymers containing polyacetylene segment are also prepared. Owing to the versatility of the anionic reactions, the present strategy can serve as a powerful tool of precise control on polymer chain microstructure, architecture, and functionalities in the same time

Continuous Production of Multiblock Copolymers in a Loop Reactor: When Living Polymerization Meets Flow Chemistry

A continuous process for the production of multiblock polymers via living anionic polymerization in a loop reactor is proposed by kinetic modeling. The process utilizes specific configurations of the loop reactors and feed inlets, thus producing multiblock polymers constituted by a blend of chains with varying number of blocks. The dependence of the product molecular parameters, such as length, composition of each block, and the block number distribution, on the residence time and the recirculation fraction is analyzed by numerical integration of differential mass balances. This dependence is subsequently translated into controllability of molecular parameters by changing the operation conditions such as the recirculation and inlet flow rates. In general, higher recirculation flow rate yields products with shorter block length but larger fraction of polymers possessing higher number of blocks and more significant compositional mixing in each block. An increase in the feed flow rates also increases the compositional mixing but gives longer block length with lower fraction of polymers possessing a higher number of blocks. While being discussed in terms of living anionic copolymerization of styrene and butadiene, the present strategy can be extended to any other living copolymerization of suitable monomer pairs, thus highlighting the use of reaction engineering to control the polymer structures

Unimolecular Micelles from Layered Amphiphilic Dendrimer-Like Block Copolymers

In this report, we synthesized layered amphiphilic dendrimer-like block copolymers containing a polystyrene core and poly­(<i>p</i>-<i>tert</i>-butoxystyrene)/poly­(<i>p</i>-hydroxylstyrene) shell (coded G4-P<i>t</i>BOS/G4-PHOS). The synthetic method is easy involving anionic polymerization, epoxidation, ring-opening reaction and hydrolysis reaction. The hydrolyzed G4-P<i>t</i>BOS was soluble in alkaline water and behaved as unimolecular micelle, as demonstrated by the results of DLS, cryo- and normal TEM, and pyrene entrapping experiment. The stability of the unimolecular micelles was investigated via ζ-potential measurements

Radical-induced oxidation of RAFT agents : a kinetic study

Radical-induced oxidn. of reversible addn.-fragmentation chain transfer (RAFT) agents is studied with respect to the effect of mol. structure on oxidn. rate. The radicals are generated by homolysis of either azobisisobutyronitrile or alkoxyamine and transformed in situ immediately into peroxy radicals through transfer to mol. oxygen. The oxidn. rate depends on the structure of Z- and R-group of thiocarbonylthio compds. For dithioesters with identical Z-Ph substituent, the oxidn. rate decreases in the order of cyanoisopropyl (-C(Me)2CN) > cumyl (-C(Me)2Ph) > phenylethyl (-CH(Me)Ph) > 2-methoxy-1-methyl-2-oxoethyl (-CH(Me) -C(=O)OCH3) > benzyl (-CH2Ph). For dithioesters with identical R-group, the oxidn. rate decreases in the order of Z = phenyl- ∼ benzyl- > RS- (trithiocarbonates) > RO- (xanthates). The stability of the RAFT agents toward oxidn. correlates well with the chain transfer abilities as those previously reported by Rizzardo and coworkers. The priority of the oxidn. reaction over the RAFT process, and the subsequent influence on RAFT polymn. are also studied. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011. [on SciFinder(R)

Dependence of Thermal Stability on Molecular Structure of RAFT/MADIX Agents : A Kinetic and Mechanistic Study

The thermal decomposition of different classes of RAFT/MADIX agents, namely dithioesters, trithiocarbonates, xanthates, and dithiocarbamates, were investigated through heating in solution. It was found that the decomposition behavior is complicated interplay of the effects of stabilizing Z-group and leaving R-group. The mechanism of the decomposition is mainly through three pathways, i.e., ?-elimination, α-elimination, and homolysis of dithiocarbamate (particularly for universal RAFT agent). The most important pathway is the ?-elimination of thiocarbonylthio compounds possessing ?-hydrogen, leading to the formation unsaturated species. For the leaving group containing solely α-hydrogen, such as benzyl, α-elimination takes place, resulting in the formation of (E)-stilbene through a carbene intermediate. Homolysis occurs specifically in the case of a universal RAFT agent, in which a thiocarbonyl radical and an alkylthio radical are generated, finally forming thiolactone through a radical process. The stabilities of the RAFT/MADIX agents are investigated by measuring the apparent kinetics and activation energy of the thermal decomposition reactions. Both Z-group and R-group influence the stability of the agents through electronic and steric effects. Lone pair electron donating heteroatoms of Z-group show a remarkable stabilizing effect while electron withdrawing substituents, either in Z- or R-group, tends to destabilize the agent. In addition, bulkier or more ?-hydrogens result in faster decomposition rate or lower decomposition temperature. Thus, the stability of the RAFT/MAIDX agents decreases in the order where R is (with identical Z = phenyl) ?CH2Ph (5) &gt; ?PS (PS-RAFT 15) &gt; ?C(Me)HPh (2) &gt; ?C(Me)2C(═O)OC2H5 (7) &gt; ?C(Me)2Ph(1) &gt; ?PMMA (PMMA-RAFT 16) &gt; ?C(Me)2CN (6). For those possessing identical leaving group such as 1-phenylethyl, the stability decreases in the order of O-ethyl (11) &gt; ?N(CH2CH3)2 (13) &gt; ?SCH(CH3)Ph (8) &gt; ?Ph (2) &gt; ?CH2Ph (4) &gt; ?PhNO2 (3). These results consort with the chain transfer acitivities measured by the CSIRO group and agree well with the ab initio theoretical results by Coote. In addition, the difference between thermal stabilities of the universal RAFT agents at neutral and protonated states has also been demonstrated. The thermal decomposition of different classes of RAFT/MADIX agents, namely dithioesters, trithiocarbonates, xanthates, and dithiocarbamates, were investigated through heating in solution. It was found that the decomposition behavior is complicated interplay of the effects of stabilizing Z-group and leaving R-group. The mechanism of the decomposition is mainly through three pathways, i.e., ?-elimination, α-elimination, and homolysis of dithiocarbamate (particularly for universal RAFT agent). The most important pathway is the ?-elimination of thiocarbonylthio compounds possessing ?-hydrogen, leading to the formation unsaturated species. For the leaving group containing solely α-hydrogen, such as benzyl, α-elimination takes place, resulting in the formation of (E)-stilbene through a carbene intermediate. Homolysis occurs specifically in the case of a universal RAFT agent, in which a thiocarbonyl radical and an alkylthio radical are generated, finally forming thiolactone through a radical process. The stabilities of the RAFT/MADIX agents are investigated by measuring the apparent kinetics and activation energy of the thermal decomposition reactions. Both Z-group and R-group influence the stability of the agents through electronic and steric effects. Lone pair electron donating heteroatoms of Z-group show a remarkable stabilizing effect while electron withdrawing substituents, either in Z- or R-group, tends to destabilize the agent. In addition, bulkier or more ?-hydrogens result in faster decomposition rate or lower decomposition temperature. Thus, the stability of the RAFT/MAIDX agents decreases in the order where R is (with identical Z = phenyl) ?CH2Ph (5) &gt; ?PS (PS-RAFT 15) &gt; ?C(Me)HPh (2) &gt; ?C(Me)2C(═O)OC2H5 (7) &gt; ?C(Me)2Ph(1) &gt; ?PMMA (PMMA-RAFT 16) &gt; ?C(Me)2CN (6). For those possessing identical leaving group such as 1-phenylethyl, the stability decreases in the order of O-ethyl (11) &gt; ?N(CH2CH3)2 (13) &gt; ?SCH(CH3)Ph (8) &gt; ?Ph (2) &gt; ?CH2Ph (4) &gt; ?PhNO2 (3). These results consort with the chain transfer acitivities measured by the CSIRO group and agree well with the ab initio theoretical results by Coote. In addition, the difference between thermal stabilities of the universal RAFT agents at neutral and protonated states has also been demonstrated

Thermal Decomposition Kinetics and Structure of Novel Polystyrene Clusters with MTEMPO as a Branching Agent

ABSTRACT: Polystyrene clusters were prepared by using a trace amount of 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine-1-oxy (MTEMPO) as a branching agent. Such clusters can undergo a thermal decomposition into linear chains at temperatures higher than 100°C. The thermal decomposition was studied by a combination of static and dynamic laser light scattering (LLS). The time dependence of the weight-average molar mass (M w), the root-mean-square z-average radius of gyration (〈R g 2 〉 z 1/2 ), and the average hydrodynamic radius (〈Rh〉) was used to monitor the decomposition kinetics and cluster structure. It has been found that Mw ∝ t -R , and the decomposition can be roughly divided into three stages; namely, from large clusters to smaller ones; from smaller clusters to less-branched ones; and finally to short linear chains. The scaling of 〈Rg〉 ∝ Mw 0.33 ( 0.01 in the first stage indicates that these clusters are uniform in density, which is rare and much different from conventional polymer clusters whose density decreases from center to periphery. Moreover, we observed, for the first time, that 〈Rg〉/〈Rh〉 ∝ Mw -0.20 ( 0.01 , revealing that even for a uniform cluster swollen in a good solvent, its periphery is still more hydrodynamically draining