Simulating　synaptic　function　and　building　brain-inspired　computers　have　received　widespread　attention.　The　memristor　is　considered　to　be　an　electronic　version　of　the　synapse　and　an　excellent　element　for　creating　a　brand-new　artificial　intelligence　system　in　the　future.　However,　most　memristor-based　electronic　synapses　currently　exhibit　low　stability　due　to　complex　resistance　switching　processes.　Based　on　a　controllable　in-situ　formation　strategy　that　we　were　able　to　employ　with　atomic　layer　deposition,　we　fabricated　electronic　synapses　based　on　Au@Al2O3　core-shell　nanoparticles.　Our　device　exhibited　extremely　reliable,　stable,　and　durable　performance　and　showed　a　capability　to　emulate　biological　synaptic　behavior,　including　synaptic　plasticity,　long-term　depression　(LTD),　long-term　potentiation　(LTP),　amplitude　dependence,　and　frequency　dependence.　This　research　provides　a　strategy　for　manufacturing　highly-reliable　electronic　synapses　for　neuromorphic　applications.