Parallel Aqueous and Nonaqueous Lithium Ion Battery Module
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Solution Overview
Problem
Battery modules with nonaqueous lithium ion batteries face issues due to variations in state of charge (SOC) between cells, leading to overcharge and rapid deterioration, especially when combined with aqueous lead storage batteries or Ni-MH batteries, which require complex protective circuits and result in high costs and heat production, and have low energy density.
Innovation Solution
A battery module configuration where both nonaqueous lithium ion batteries and aqueous lithium ion batteries are connected in parallel, with the aqueous LIBs maintaining a constant voltage to prevent overcharge of nonaqueous LIBs, allowing for simplified protective circuits and maintaining high energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If nonaqueous LIBs are connected in series to form a battery module, then the battery module can provide higher voltage and energy density, but variations in SOC between cells may cause overcharge and fast deterioration
Solution Approach 1:
An aqueous lithium ion battery is introduced as an intermediary component connected in parallel with each nonaqueous LIB. This aqueous battery acts as a mediator that absorbs excess charge when the nonaqueous LIB reaches full charge, preventing overcharge while maintaining the high voltage and energy density of the series-connected nonaqueous LIBs.
2Reliability
If a protective circuit is added to balance SOC variations between nonaqueous LIBs, then overcharge can be prevented, but the circuit becomes complicated and costs increase
Solution Approach 1:
The aqueous lithium ion battery serves as a passive intermediary that automatically balances SOC variations through voltage equalization. When nonaqueous LIBs have different SOC levels, the aqueous battery provides a voltage reference that prevents overcharge of individual cells, eliminating the need for complex active protective circuits with multiple sensors and control elements.
Solution Approach 2:
The aqueous lithium ion battery automatically performs the protective function through its inherent electrochemical properties. The system self-regulates by allowing current to flow through the aqueous battery when voltage differences exist between parallel-connected nonaqueous LIBs, balancing their SOC levels without requiring external control systems.
3Reliability
If aqueous lead storage batteries or Ni-MH batteries are used in parallel with nonaqueous LIBs, then overcharge protection is achieved, but energy density decreases due to low operating electric potential
Solution Approach 1:
The patent changes the key parameter of the protective battery from traditional aqueous lead storage or Ni-MH batteries to aqueous lithium ion batteries. This parameter change increases the operating electric potential of the protective battery to match that of the nonaqueous LIBs, thereby maintaining high energy density while providing overcharge protection through parallel connection.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively suppresses overcharge of nonaqueous LIBs, maintains high energy density, and extends the battery module's lifespan without complicating the protective circuit design, ensuring stable operation and reduced production costs.
Implementation Method 1
aqueous lithium ion batteries connected in parallel to the nonaqueous lithium ion battery, with the aqueous lithium ion battery maintaining a constant voltage to prevent overcharge
Data Source
AI summary
According to one embodiment, a battery module includes a battery unit. The battery unit includes a nonaqueous lithium ion battery including a nonaqueous electrolyte, and an aqueous lithium ion battery including an electrolytic solution in which an electrolyte is dissolved in an aqueous solvent. In the battery unit, the aqueous lithium ion battery is connected in parallel to the nonaqueous lithium ion battery.