High conductive transition metal chalcogenides with larger theoretical capacities are considered as promising candidates in electrochemical energy storage filed. Unfortunately, the sluggish kinetics of Li-ion transport and severe volume change still hinder their practical application. Here, mesocrystal Cu2-xSe nanoplates are designed and synthesized through a facile solvothermal method with the assistance of sodium tartrate. The formation mechanism of the mesocrystal Cu2-xSe is put forward based on the structure-evolution investigations. The Cu2-xSe nanoplates with mesoporous structure can accommodate the volume change, increase the contact area between the electrode and electrolyte, promote the kinetics of Li-ion transport and improve the infiltration of the electrode. Benefit from these advantages, the mesocrystal Cu2-xSe nanoplates display better electrochemical performance. As anode for lithium ion batteries, the mesocrystal Cu2-xSe nanoplates exhibit the specific capacity of 427 mAh g−1 after 100 cycles at current density of 100 mA g−1. At high current density of 1000 mA g−1, a specific capacity as high as 164 mAh g−1 can be achieved after 400 cycles. When evaluated for electrochemical supercapacitors, it displays a pseudocapacitance of 495.6 F g−1 at a current density of 1 A g−1 and long-term cycle life of ≈81.3 % capacity retention after 2000 cycles.