Trace-Element Ternary Cathode Sheet for High-Temperature Cycling
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Solution Overview
Problem
Lithium ion batteries face challenges in cycle performance at high temperatures due to thermal expansion of positive electrode materials, leading to decreased capacity and increased internal resistance, particularly with high nickel ternary materials which have limited commercial application.
Innovation Solution
A positive electrode sheet with a ternary positive electrode material containing trace elements like boron, zirconium, and aluminum, where the content and distribution of these elements are controlled to satisfy specific equations related to diffraction peak breadth, particle size distribution, and mass proportion, enhancing stability and cycling performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If high nickel ternary positive electrode materials are used to increase capacity and energy density, then the theoretical capacity is improved, but the stability of the material deteriorates
Solution Approach 1:
The patent introduces trace elements (boron, zirconium, aluminum) at specific local positions within the ternary positive electrode material structure. These trace elements are doped into specific crystallographic sites to locally modify the material properties, enhancing structural stability without significantly reducing the overall high capacity provided by the high nickel content. This local modification approach allows the material to maintain both high capacity and improved stability.
Solution Approach 2:
The patent creates a composite structure by combining high nickel ternary material with trace amounts of boron, zirconium, and aluminum elements. This composite approach leverages the high capacity of nickel while incorporating stabilizing effects from the trace elements. The synergistic combination results in a material that achieves both high energy density and improved structural stability during cycling.
2Use of energy by moving object
If the discharge cut-off voltage is increased to increase energy density, then the energy density is improved, but the capacity decay accelerates and internal resistance increases excessively
Solution Approach 1:
The patent modifies the electrochemical parameters of the positive electrode material by introducing trace elements that alter the material's voltage profile and electrochemical stability. The trace elements shift the operating voltage range and improve the material's ability to withstand high voltage stress, enabling sustained operation at higher discharge cut-off voltages without excessive capacity decay or internal resistance increase. This parameter modification allows the battery to achieve higher energy density with maintained cycle life.
3Temperature
If high temperature operation is endured to meet application requirements, then the operating temperature range is expanded, but the lattice structure undergoes thermal expansion resulting in decreased capacity and increased internal resistance
Solution Approach 1:
The patent incorporates trace elements that act as thermal buffers within the crystal structure, providing beforehand cushioning against thermal expansion effects. These trace elements create a more thermally stable lattice structure that resists expansion at elevated temperatures, thereby preserving capacity and preventing excessive internal resistance increase during high temperature operation. The trace elements essentially pre-compensate for thermal stress before it can cause significant 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 controlled content and distribution of trace elements improve the stability and cycling performance of lithium ion batteries at high temperatures, reducing internal resistance growth and maintaining high capacity retention rates under high voltage and temperature conditions.
Implementation Method 1
In a high-temperature environment, the positive electrode material of the battery may undergo thermal expansion of the lattice structure, resulting in a decrease in the capacity of the battery and an increase in the internal resistance
Implementation Method 2
F101 is a half-peak breadth, in the unit of °, of a diffraction peak at a position where a diffraction angle 2θ is 36.6±1° in an XRD spectrum of the positive electrode active material
Data Source
AI summary
The present invention discloses a positive electrode sheet, an electrochemical device including the positive electrode sheet, and an electronic device. The positive electrode sheet of the present invention includes a positive electrode current collector and a positive electrode active material layer, wherein the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes a ternary positive electrode material containing boron, zirconium and aluminum; the positive electrode sheet satisfies an equation as follows: 11.0≤[F101+(DFW/4.5)]×1.85±ln(M)≤17.0; where F101 is a half-peak breadth of a diffraction peak of the positive electrode active material at a position of 36.6±1° in an XRD spectrum; DFW is a full width at half maximum of particle size volume distribution of the positive electrode active material; and M is a total mass proportion of the trace elements in the positive electrode active material.