TECHNOLOGY FOCUS - ELECTRONICS - Preferred Components: The electrochemical cell comprises unit for connecting electrochemical cell to outside electrical load or charging unit.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Composition: The electrode (101) is negative electrode comprising carbon, graphite, coke, lithium titanate, lithium-tin alloy, silicon and/or carbon-silicon composite. The electrode (102) is positive electrode, comprising lithium cobalt oxide, lithium iron phosphate, lithium nickel oxide, lithium manganese phosphate, lithium cobalt phosphate, Li(Mn1/3Ni1/3Co1/3)O2(MNC), Li(Ni1yzCoyAlz)O2(NCA) and/or lithium manganese oxide. The electrodes (101) and (102) have same material composition.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: The aromatic dianhydride is chosen from pyromellitic dianhydride, biphenyltetracarboxylic dianhydride and/or 3,3',4,4'-benzophenone tetracarboxylic dianhydride. The aromatic diamine is chosen from oxydianiline, 1,3-bis(4-aminophenoxy)benzene and/or 1,4-phenelenediamine. The reactive end-capper is functionalized anhydride or functionalized amine, functionalized with reactive functionality chosen from acetylene, vinyl, epoxide, nitrile and ester. The reactive end-capper is acetylene-functionalized phthalic anhydride chosen from phenylethynylphthalic anhydride, ethynyl phthalic anhydride, pyromellitic ethynyl phthalic anhydride and methyl ethynyl phthalic anhydride.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The cross-linked polyimide comprises cyclotrimerized aromatic polyimide of formula (I), preferably 1,3,5-tripolyimide benzene, 1,3,5-tripolyimide-2,4,6-triphenyl benzene, 1,3,5-tripolyimide-2,4,6-trimethyl benzene and/or 1,3,5-tripolyimide-2,4,6-(isobenzofuran-1 ,3-dione). The molar ratio of aromatic dianhydride, aromatic diamine and acetylene-functionalized phthalic anhydride is 0.85:1:0.30-0.95:1:0.01, preferably 0.88:1:0.24-0.95:1:0.02.R"=H, methyl, phenyl or phthalic anhydride;R'=group of formula (a) or (b);andR= acetylene, ethynyl benzene, 3-phenyl-2-propynal, ethynyl phthalic anhydride or propyne.Preferred Properties: The break stress of nanoweb is at least 200 kg/cm2, preferably 330 kg/cm2. The number average diameter of nanofiber is 1000 nm or less, preferably 100-400 nm.