Electrodeposited <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>Co</mml:mi></mml:math>-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>Ni</mml:mi></mml:math> layered double hydroxid

With the rapid development of data science, higher performance hardware, such as resistive-switching memory with alternative ultrathin materials, emerges. Although the dielectric constant is an important parameter for photoelectric devices, its tunability in a thin film is needed, a method for its measurement in an ultrathin film is lacking, and its relationship with resistive-switching behavior is rarely investigated. Here, a dielectric-property-tunable thickness-controllable continuous $\mathrm{Co}$-$\mathrm{Ni}$ layered double hydroxide (LDH) film is achieved by bulk-phase doping of polyvinyl alcohol (PVA) using an electrodeposition method, and a general method for dielectric constant measurement of a thin film based on a parallel-plate capacitor is suggested. The $\mathrm{Co}$-$\mathrm{Ni}$ LDH-PVA significantly suppresses dielectric loss by 99%, and an enhanced resistive-switching performance is achieved with an increased initial resistivity, a suppressed leakage current, a reduced set power by 79%, a data retention over ${10}^{4}$ s, an endurance up to 200 cycles, and a synapselike capability, compared with pure LDH material. The enhanced electrical performance comes from an improved inherent trade-off of dielectric constants inside an electrodeposited LDH film that is tuned by PVA; this is supported by density-functional calculations. This work provides a reference for the selection and modification of resistive-switching materials in relation to dielectric constants.