System and method for determining degradation of rechargeable lithium ion battery

A system for determining degradation of a rechargeable lithium ion battery, comprising:

• a degradation parameter acquisition unit operative to perform a degradation diagnosis based on an open circuit voltage characteristic of said rechargeable lithium ion battery indicating how said rechargeable lithium ion battery varies in open circuit voltage as said battery varies in capacity to obtain a capacity ratio of a positive electrode of said rechargeable lithium ion battery, a capacity ratio of a negative electrode of said rechargeable lithium ion battery, and a battery capacity fluctuation amount;
• a lithium deposition estimation unit operative to apply said capacity ratios respectively of said positive and negative electrodes that are obtained to a previously obtained correspondence between said capacity ratios respectively of said positive and negative electrodes and a first amount of said battery capacity fluctuation amount to separate said battery capacity fluctuation amount that is obtained into said first amount and a second amount of said battery capacity fluctuation amount, said first amount corresponding to degradation attributed to wear, said second amount corresponding to degradation attributed to deposition of lithium;
• and
• a determination unit operative to determine whether said rechargeable lithium ion battery is reusable/recyclable based on at least one of:
• said capacity ratios respectively of said positive and negative electrodes obtained by said degradation parameter acquisition unit;
• and said second amount calculated by said lithium deposition estimation unit;
• said capacity ratio of said positive electrode being represented by a ratio of a capacity of said positive electrode with said rechargeable lithium ion battery in a degraded state to a capacity of said positive electrode with said rechargeable lithium ion battery in an initial state,
• said capacity ratio of said negative electrode being represented by a ratio of a capacity of said negative electrode with said rechargeable lithium ion battery in said degraded state to a capacity of said negative electrode with said rechargeable lithium ion battery in said initial state,
• said battery capacity fluctuation amount being indicated by a product of said capacity of said negative electrode in said degraded state and an amount of a deviation of an axis of a composition of said negative electrode relative to an axis of a composition of said positive electrode in said degraded state.