Lithium Storage Element Using Pitch Coal Deposited on Activated Carbon
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Solution Overview
Problem
Current lithium ion capacitors face challenges in achieving high energy density, high output characteristics, and durability, particularly in maintaining these properties when the negative electrode active material layer is made thinner and the capacitor volume is reduced.
Innovation Solution
A nonaqueous lithium storage element is developed with a negative electrode active material layer containing a composite porous material where pitch coal is deposited on activated carbon, with a specific weight ratio and softening point, and doped with lithium ions within a certain range, enhancing both energy density and durability while maintaining high output characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the negative electrode active material layer is made thinner to reduce capacitor volume, then the volume is reduced, but the energy density and durability deteriorate
Solution Approach 1:
The patent employs activated carbon with a porous structure as the negative electrode active material. The porous structure provides a large internal surface area that can accommodate lithium ions, enabling high energy density even in a thin layer. The pores allow efficient lithium ion transport while maintaining high capacitance per unit volume, thus achieving high energy density without requiring a thick electrode layer.
Solution Approach 2:
The patent uses a composite structure combining activated carbon with conductive additives and binding agents to create the negative electrode active material layer. This composite approach enhances the overall performance by improving electrical conductivity, mechanical strength, and lithium ion accessibility while maintaining a thin profile, thereby achieving high energy density in a reduced volume.
2Volume of moving object
If the negative electrode active material layer is made thinner to reduce capacitor volume, then the volume is reduced, but the output characteristics deteriorate
Solution Approach 1:
The porous structure of activated carbon provides numerous pathways for lithium ion transport, enabling rapid charge and discharge rates. The high surface area to volume ratio within the pores facilitates efficient ion exchange, maintaining high output characteristics even when the overall electrode layer is thin, thus achieving high power density in a compact volume.
Solution Approach 2:
The patent optimizes the local properties of the negative electrode active material by controlling the pore size distribution, surface chemistry, and material composition within the electrode layer. This local optimization ensures that lithium ion transport and electrochemical reactions occur efficiently throughout the thin layer, maintaining high output characteristics without requiring increased thickness.
3Volume of moving object
If the negative electrode active material layer is made thinner to reduce capacitor volume, then the volume is reduced, but the durability deteriorates
Solution Approach 1:
The composite structure includes binding agents and conductive additives that provide mechanical strength and structural integrity to the thin electrode layer. This composite approach prevents material degradation and maintains electrode stability during repeated charge/discharge cycles, ensuring high durability even when the electrode layer is thin and the capacitor volume is reduced.
Solution Approach 2:
The porous structure of activated carbon accommodates volume changes during lithium ion insertion and extraction, reducing mechanical stress on the electrode material. This structural flexibility prevents cracking and degradation over time, maintaining durability in thin electrode layers where mechanical failures would be more critical.
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
The solution achieves compatibility of high energy density, high output characteristics, and durability, allowing for efficient lithium charge/discharge processes even with a thinner negative electrode active material layer and reduced capacitor volume.
Implementation Method 1
thermally reacting the activated carbon with the pitch in an inert atmosphere, to produce the composite porous material in which the pitch coal is deposited on the surface of the activated carbon
Implementation Method 2
produce the composite porous material in which the pitch coal is deposited on the surface of the activated carbon
Implementation Method 3
doped with lithium ions within a certain range
Implementation Method 4
initial-time lithium charge/discharge characteristics satisfy: charging amount is 1100 mAh/g to 2000 mAh/g, and discharging amount is 100 mAh/g or higher at a negative electrode potential of 0 to 0.5 V
Implementation Method 5
a carbonaceous material is a carbon material capable of accommodating/releasing lithium in an ionized state
Implementation Method 6
composite porous material having a pitch coal deposited on the surface of an activated carbon
Data Source
Figure 1(a)~1(b)
Figure 2~3
Figure 4
AI summary
Provided is a nonaqueous lithium storage element which is obtained by housing an electrode body and a nonaqueous electrolyte solution containing a lithium salt in an outer case, said electrode body being composed of a negative electrode that is composed of a negative electrode collector and a negative electrode active material layer laminated on one or both surfaces of the negative electrode collector, a positive electrode that is composed of a positive electrode collector and a positive electrode active material layer laminated on one or both surfaces of the positive electrode collector, and a separator. This nonaqueous lithium storage element is characterized in that the features (1) and (2) described below are satisfied at the same time with respect to the initial lithium charge/discharge characteristics of a negative electrode active material that is contained in the negative electrode active material layer. (1) The amount of charge is from 1,100 mAh/g to 2,000 mAh/g (inclusive). (2) The amount of discharge is 100 mAh/g or more at the negative electrode potential of 0-0.5 V.