Lithium Cobaltate Cathode Morphology for High-Voltage Cycle Stability
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Solution Overview
Problem
The challenge is to enhance the compaction density and cycle performance of lithium cobaltate batteries, which suffer from irreversible phase transitions and poor conductivity at high charging voltages, leading to accelerated capacity attenuation and structural destruction.
Innovation Solution
A positive electrode piece with a regular morphological structure and accordion stacking, utilizing a lithium cobaltate active material with specific crystal phases and doping elements, treated by cross-section polishing and ion exchange reactions, to improve compaction density and conductivity, and assembled into a battery with enhanced structural stability and multiple platform voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium cobaltate is used as positive electrode active material with charging voltage ≥ 4.55V, then battery energy density is improved, but irreversible phase transition from O3 to H1-3 occurs leading to poor ionic conductivity and electronic conductivity
Solution Approach 1:
The patent modifies the crystal structure parameters of lithium cobaltate by controlling the ratio of peak intensities (101)/(004) to be ≥1.5, which changes the interlayer spacing and electronic structure. This parameter change allows the material to maintain stability at high charging voltages ≥4.55V without undergoing harmful phase transitions, thereby preserving both ionic and electronic conductivity while enabling high energy density operation
Solution Approach 2:
The patent creates a composite structure by doping lithium cobaltate with other elements to form a multi-element oxide with formula Li1+n-xA1-xCo1-yB2yO3. This composite approach combines the high voltage characteristics of lithium cobaltate with the stabilizing effects of dopant elements, achieving both high energy density and maintained conductivity through synergistic material composition
2Quantity of substance
If charging voltage is increased to ≥ 4.55V to improve energy density, then capacity is improved, but capacity attenuation is accelerated due to structure destruction
Solution Approach 1:
The patent applies beforehand cushioning by pre-modifying the lithium cobaltate crystal structure through controlled peak intensity ratios and doping before high-voltage charging. This preparatory structural adjustment creates a more stable framework that cushions against the damaging effects of high-voltage operation, preventing rapid capacity attenuation and extending cycle life while maintaining high discharge capacity
Solution Approach 2:
The patent converts the potentially harmful high-voltage stress into a beneficial effect by designing the crystal structure with specific peak intensity ratios ≥1.5 and doping compositions. The high voltage that would normally cause destructive phase transitions instead promotes beneficial structural ordering and activates high-capacity electrochemical reactions, transforming the harmful stress into enhanced capacity while maintaining cycle stability
3Ease of manufacture
If conventional lithium cobaltate structure is used, then manufacturing is simple, but compaction density is limited and cannot be improved further
Solution Approach 1:
The patent changes the crystallographic parameters of lithium cobaltate by controlling the peak intensity ratio (101)/(004) to be ≥1.5 and adjusting doping compositions. These parameter changes result in a denser crystal packing arrangement that achieves higher compaction density (≥3.95g/cm³) while maintaining manufacturing simplicity through conventional solid-state synthesis methods and straightforward doping procedures
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 results in higher discharge capacity, stable structure, and improved cycle performance of the battery, with increased compaction density and conductivity, effectively addressing the limitations of conventional lithium cobaltate batteries.
Implementation Method 1
utilizing a lithium cobaltate active material with specific crystal phases and doping elements, treated by cross-section polishing and ion exchange reactions
Data Source
Figure 1
AI summary
The present application provides a positive electrode piece, a battery and an electric device. A first aspect of the present invention provides a positive electrode piece, the positive electrode piece includes a positive electrode current collector and a positive electrode active layer provided on at least one surface of the positive electrode current collector, and the positive electrode active layer includes a positive electrode active material; in a plane composed of a length direction and a thickness direction of the positive electrode piece, particles of the positive electrode active material have a longest distance a in the length direction of the positive electrode piece, and have a longest distance b in the thickness direction of the positive electrode piece, and in a region not less than 25µm∗25µm, the number of the particles of the positive electrode active material meeting a/b≥3 is N, where N≥2. The positive electrode active material provided by the present invention has a relatively regular morphological structure and is easy to form an accordion stacking structure, which is helpful to improve structural integrity of the positive electrode active material, thereby improving the compaction density of the positive electrode piece and the cycle performance of the battery.