Carbon Anode Material for Lithium-Ion Hybrid Capacitor Cycling Stability
Solution Overview
Problem
Lithium-ion batteries and lithium-ion hybrid capacitors face poor cycling characteristics and degradation of anode performance over numerous charging/discharging cycles, particularly in lithium-ion hybrid capacitors, which limits their efficiency and lifespan.
Innovation Solution
A carbon material with specific properties, including a particle size range of 1 to 15 μm, bulk density of 0.3 to 1.2 g/cc, surface area not exceeding 10 m2/g, and low impurity content, is used to fabricate anodes, which are carbonized in an inert gas environment and optionally graphitized at elevated temperatures, maintaining high purity and hardness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If graphite materials are used for anodes in lithium-ion hybrid capacitors, then the device can achieve lithium-ion battery and lithium-ion hybrid capacitor functionality, but the cycling characteristics deteriorate and anode performance degrades after numerous charging/discharging cycles
Solution Approach 1:
The patent applies parameter changes by precisely controlling particle size (d50: 1-15 μm), bulk density (0.3-1.2 g/cc), surface area (≤10 m2/g), and impurity content (<3000 ppm) of the carbon material to resolve the contradiction between achieving lithium-ion functionality and maintaining cycling stability. These parameter optimizations prevent performance degradation while preserving the electrochemical functionality required for lithium-ion insertion and extraction cycles.
2Ease of manufacture
If carbonized particles are heated to elevated temperatures (2000° C. or higher) to produce graphite particles, then the carbon material becomes suitable for anode fabrication, but the cycling characteristics and anode performance retention worsen
Solution Approach 1:
The patent resolves this contradiction by optimizing the graphitization temperature parameter within a specific range (1500-2500°C) rather than using excessively high temperatures. This controlled thermal treatment produces graphitic carbon with appropriate crystallinity and structure for anode fabrication while avoiding the performance degradation associated with overheating, thus maintaining both manufacturability and cycling reliability.
3Power
If the anode is pre-doped with lithium ions to achieve high output voltage, then the voltage increases, but the anode performance degrades after numerous cycles
Solution Approach 1:
The patent applies preliminary action by pre-doping the carbon anode with lithium ions during the manufacturing process rather than relying on subsequent cycling to achieve doping. This initial lithium ion incorporation establishes the desired voltage characteristics from the start while the optimized carbon material properties ensure that this pre-doped state remains stable throughout extended cycling, preventing performance degradation.
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 carbon material-based anodes exhibit superior cycling characteristics, retaining capacitance within 5% of initial values and equivalent series resistance increase of less than 20% after 100,000 cycles, ensuring sustained high-performance operation without significant degradation.
Implementation Method 1
carbonizing a carbonizable precursor material in an inert gas environment to thermally convert the precursor material to the carbon material
Implementation Method 2
These carbonized particles then can be heated to elevated temperature, which may be on the order of 2000° C. or higher, to produce graphite particles suitable for fabrication of the anode
Data Source
AI summary
A carbon material is described, having utility for fabricating an electrode of an electrochemical energy device, wherein the carbon material includes a particulate carbon having a particle size d50 in a range of from 1 to 15 μm, a bulk density in a range of from 0.3 g/cc to 1.2 g/cc, a surface area as measured by nitrogen BET surface area determination at 25° C. that does not exceed 10 m2/g, and an impurity content of less than 3000 ppm by weight, based on weight of the carbon material. Such carbon material may be utilized in amorphous or graphitic form in an electrode of an electrochemical energy device, such as a negative electrode of a lithium-ion battery or a lithium-ion hybrid capacitor.