Secondary Lithium Ion Cell Voltage Adjustment
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Solution Overview
Problem
The limitation of charge cut-off voltage in lithium ion batteries restricts the actual utilization of active electrode materials, preventing the achievement of higher capacity and average operating voltage, despite advancements in positive and negative electrode materials, due to structural changes and electrolyte decomposition at voltages above 4.2V.
Innovation Solution
Elevating the charge cut-off voltage to between 4.2V and 5.8V and adjusting the ratio of positive to negative electrode material within a specific range, while using a protecting circuit with overcharging protection and release voltages above 4.35V and 4.15V respectively, to enhance specific energy, capacity, and average operating voltage without compromising recycle life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the charge cut-off voltage is increased above 4.2V to improve capacity and average operating voltage, then the specific energy and capacity increase, but the positive electrode material undergoes structure change and the electrolyte decomposes, adversely affecting recycle life
Solution Approach 1:
The patent changes the charge cut-off voltage parameter from the conventional limit of 4.2V to a higher range of 4.25V-5.8V, thereby increasing the specific energy and capacity of the lithium ion battery while maintaining acceptable recycle life through protective measures
Solution Approach 2:
The patent applies preliminary protective actions by introducing a protecting circuit with overcharge protection function before the battery reaches dangerous voltage levels. The protecting circuit prevents excessive voltage that would cause severe structure changes and electrolyte decomposition, thus preserving recycle life while allowing higher operating voltages
2Reliability
If the charge cut-off voltage is limited to below 4.2V to maintain structure stability and prevent electrolyte decomposition, then the recycle life is preserved, but the actual utilization rate of active electrode materials is restricted
Solution Approach 1:
The patent changes the voltage parameter from the conservative limit of 4.2V to a higher operational range of 4.25V-5.8V, thereby increasing capacity utilization of active electrode materials while implementing protective mechanisms to maintain structure stability and prevent excessive electrolyte decomposition
Solution Approach 2:
The patent implements a feedback mechanism through the protecting circuit that continuously monitors the battery voltage and activates protective measures when the voltage approaches dangerous levels. This feedback control allows the battery to operate at higher voltages for improved capacity while automatically preventing conditions that would severely damage structure and reduce recycle life
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 approach significantly increases specific energy and average operating voltage while maintaining excellent recycle properties, achieving up to 30% increase in specific energy with minimal impact on recycle life, even at higher charge cut-off voltages, and is applicable to both single cells and batteries.
Implementation Method 1
a protecting circuit having a first overcharging protection voltage of greater than 4.35 V, and an overcharge release voltage of greater than 4.15 V
Implementation Method 2
the electrolyte may decompose
Implementation Method 3
lithium cobalt oxides as a positive electrode material of secondary lithium ion cell has a theoretical capacity of 248 mAh/g
Data Source
AI summary
The present invention provides a new method for improving capacity, average operating voltage and specific energy of a secondary lithium ion cell or battery. This method is achieved by means of properly adjusting the ratio between a positive material and negative material, which is calculated by theoretical specific energy, and properly increasing charge cut-off voltage. The present method can greatly increasing specific energy and average operating voltage of a secondary lithium ion cell without influence on recycle property of the cell. The present invention also provides a secondary lithium ion cell or battery practicing the method, a protecting circuit adapted for the secondary lithium ion cell or battery, a electronic device using said protecting circuit and said secondary lithium ion cell or battery, and a charging device for the secondary lithium ion cell or battery.