State determination device for lithium-ion rechargeable battery

A state determination device for a lithium-ion rechargeable battery, comprising:

• a storage device;
• and
• an execution device, wherein
• the storage device stores deposition determination mapping data,
• the deposition determination mapping data is data for defining a deposition determination mapping;
• the deposition determination mapping is mapping that uses a difference variable as an input variable and outputs information on whether lithium is deposited on a negative electrode of the lithium-ion rechargeable battery;
• the difference variable is a variable indicating information on a difference between a surface concentration of the negative electrode active material and an average concentration of the negative electrode active material in the lithium-ion rechargeable battery;
• the execution device is configured to execute a determination acquisition process and a determination process;
• the determination acquisition process is a process for acquiring a value of the input variable of the deposition determination mapping;
• and
• the determination process is a process for determining deposition of lithium by inputting the value of the input variable of the deposition determination mapping to the deposition determination mapping.