Non-aqueous secondary batteries, such as lithium ion secondary batteries, are small and light, high in energy density, and capable of repeated cycles of charge and discharge. For such characteristics, secondary batteries are used in a wide variety of applications. Therefore, in recent years, various studies have been made to achieve further improvements in the performance of non-aqueous secondary batteries.
Specifically, for example, PTL 1 and other literatures propose a technique of improving electrical characteristics of a non-aqueous secondary battery by integrating together electrodes and separators by bonding with adhesive layers to suppress cell bulging and increases in interelectrode distance which are associated with repeated cycles of charge and discharge.
Exemplary electrodes to be bonded with separators with adhesive layers in non-aqueous secondary batteries such as lithium ion secondary batteries include those prepared by forming an electrode mixed material layer on a current collector, and those prepared by further providing a reinforcing porous membrane layer on the mixed material layer formed on the current collector. Exemplary separators to be bonded to electrodes with adhesive layers include those prepared by providing the surface of a porous separator substrate with a porous membrane layer which is directed to improve heat resistance and strength.
The electrode mixed material layer of an electrode is formed for example by applying onto a current collector an aqueous slurry composition for electrode containing for example electrode active material particles and a water-soluble polymer which exerts thickening and binding effects, and drying the slurry composition for electrode applied. The porous membrane layer provided on the electrode mixed material layer or separator substrate is formed for example by applying onto the electrode mixed material layer or separator substrate an aqueous slurry composition for porous membrane layer containing for example non-conductive particles and a water-soluble polymer which exerts thickening and binding effects, and drying the slurry composition for porous membrane layer applied.