Multi-Step Li-Ion Charging for Low-Temperature Plating
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Solution Overview
Problem
Conventional charging techniques for lithium rechargeable batteries, such as constant-current methods, lead to lithium plating at low temperatures, unbalanced cell stacks, shortened cycle life, and unsafe conditions due to internal shorts, particularly at low temperatures.
Innovation Solution
A multi-step charging technique involving alternating constant-current and constant-voltage steps, with parameters adjusted based on battery temperature, to prevent lithium plating and ensure balanced charging, thereby enhancing cycle life and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If constant-current charging is used, then charging speed is improved, but lithium plating occurs at low temperatures
Solution Approach 1:
The charging current is dynamically adjusted based on temperature conditions. The system transitions from a static constant-current approach to a dynamic multi-step approach where current magnitude changes according to real-time temperature feedback, preventing lithium plating while maintaining charging efficiency
Solution Approach 2:
The charging parameters (current and voltage) are changed based on temperature conditions. The system implements temperature-dependent parameter adjustment, using different current levels for different temperature ranges to avoid lithium plating at low temperatures while maintaining fast charging at higher temperatures
2Loss of time
If conventional charging techniques are used, then charging time is reduced, but cell balance deteriorates
Solution Approach 1:
The system implements feedback control by monitoring individual cell voltages and currents during charging. Based on this feedback, the charging algorithm adjusts current distribution to maintain cell balance, preventing overcharging of weaker cells while ensuring complete charging of the stack
Solution Approach 2:
The charging process is segmented into multiple steps with different current levels. The multi-step charging profile allows different portions of the cell stack to be charged at appropriate rates, maintaining balance while reducing overall charging time compared to conservative single-rate charging
3Productivity
If high current charging is applied, then charging efficiency is improved, but internal short formation increases
Solution Approach 1:
The charging current is dynamically controlled based on real-time monitoring of cell conditions. The system adjusts current magnitude to optimize charging efficiency while preventing conditions that lead to internal shorts, particularly by avoiding excessive current at temperatures where lithium plating risk is high
Data Source
AI summary
Some embodiments of the present invention provide a system that charges a battery. During operation, the system obtains a set of charging currents {I1, . . . , In} and a set of charging voltages {V1, . . . , Vn}. Next, the system repeats constant-current and constant-voltage charging operations, starting with i=1 and incrementing i with every repetition, until a termination condition is reached. These constant-current and constant-voltage charging operations involve charging the battery using a constant current Ii until a cell voltage of the battery reaches Vi, and then charging the battery using a constant voltage Vi until a charging current is less than or equal to Ii+1.