Composite Positive Electrode Plate for Cycle and Thickness Stability
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Solution Overview
Problem
Existing secondary batteries face challenges in cycle performance, energy density, low-temperature discharge capacity retention, and high-temperature storage performance, necessitating improvements for wider applications in energy storage and mobility sectors.
Innovation Solution
A positive electrode plate comprising two active materials, Li x Ni y Co z M k Me p O r E s and Li a A b Mn 1-c B c P 1-d R d O 4-n D n, with controlled particle sizes and specific surface areas, limits thickness change during charging and discharging, enhancing electronic and ionic conductivity, and optimizing compaction density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single positive electrode active material is used, then the electrode structure is simple, but the cycle performance and thickness stability are poor
Solution Approach 1:
The patent uses a composite positive electrode active material comprising Li-rich layered oxide and Ni-rich layered oxide. The Li-rich layered oxide (Li1.2Mn0.54Co0.13Ni0.1Mn0.03)O2 provides high capacity and volume expansion compensation, while the Ni-rich layered oxide LiNixCoyMn1-y-zMzO2 (where M is one or more of Al, Ti, V, or Cr) provides high voltage and structural stability. This composite structure resolves the contradiction by combining materials with complementary properties to achieve both high reliability and controlled complexity.
2Quantity of substance
If high-capacity materials are used to increase energy density, then the gram capacity increases, but the thickness change during charge-discharge becomes excessive
Solution Approach 1:
The patent optimizes the composition parameters of the composite material, specifically controlling the ratio of Li-rich to Ni-rich layered oxide, the doping elements (Al, Ti, V, Cr), and the particle size distribution (Dv50: 3-10 μm, Dv99: <30 μm). These parameter changes enable the material to achieve high gram capacity (≥150 mAh/g) while limiting thickness change to 5-15% during full charge-discharge cycles, resolving the contradiction between capacity and stability.
3Speed
If particle size is reduced to improve kinetics, then ionic conductivity improves, but specific surface area increases leading to more side reactions
Solution Approach 1:
The patent optimizes the particle size parameters to Dv50 of 3-10 μm and Dv99 of less than 30 μm, achieving a balance between ionic conductivity and side reaction suppression. Additionally, a coating layer containing one or more of Li3PO4, Li2SiO3, Li2SiO2N, or Al2O3 is applied on the particle surface, which reduces side reactions while maintaining good ionic conductivity by providing a stable interface between the electrode material and electrolyte.
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
Improves energy density, cycle performance, low-temperature discharge capacity retention, and high-temperature storage performance by stabilizing the electrode structure and reducing lithium ion diffusion impedance.
Implementation Method 1
two positive electrode active materials are both used, and a thickness change degree of the positive electrode plate between a fully-charged state and a fully-discharged state is limited by different volume change rates of the two positive electrode active materials during charge and discharge
Implementation Method 2
By controlling the particle sizes, diffusion paths of lithium ions in the positive electrode plate are shortened, bulk diffusion impedance of the lithium ions in the positive electrode plate is reduced
Implementation Method 3
the first positive electrode active material includes a core and a coating layer coating the core
Data Source
Figure 1~3
Figure 4~6
AI summary
A positive electrode plate, a battery, and an electrical device. The positive electrode plate includes a first positive electrode active material and a second positive electrode active material, where the first positive electrode active material includes a compound LixNiyCozMkMepOrEs, and the second positive electrode active material includes a compound LiaAbMn1-cBcP1-dRdO4-nDn, where the following is satisfied: