Lithium Secondary Battery Electrode Balancing for Longer Cycle Life
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Solution Overview
Problem
Existing lithium-ion batteries face challenges in achieving long life span despite optimizations in positive and negative electrode materials, electrolyte solutions, and separator materials.
Innovation Solution
A lithium secondary battery design that includes a positive electrode plate with a Li1+aM1bFe1-cAcP1-dEdO4 active material and a negative electrode plate with graphite, optimized by controlling parameters such as areal density, reversible lithium capacity, first lithiation capacity, and electrolyte solution conductivity to satisfy specific equations, enhancing cycling performance and extending service life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If conventional electrode materials, electrolyte solutions, and separator materials are used with standard optimizations, then manufacturing cost and ease of manufacture are maintained, but battery life and cycling performance are insufficient
Solution Approach 1:
The patent applies parameter changes by precisely controlling the areal density of the positive-electrode active material layer (CWc) and the reversible lithium capacity parameters (Da, Ca, Dc) to satisfy specific mathematical relationships. It also controls the conductivity of the electrolyte solution (ρ) within a specific range. These parameter optimizations enable the battery to achieve extended service life and improved cycling performance while maintaining manufacturing feasibility through quantitative control rather than qualitative material changes.
2Use of energy by moving object
If the areal density of the positive-electrode active material layer is increased to improve capacity, then energy density is improved, but cycle life deteriorates due to excessive material loading
Solution Approach 1:
The patent resolves this contradiction by establishing specific mathematical relationships between the areal density of the positive-electrode active material layer (CWc) and the reversible lithium capacity parameters (Da, Ca, Dc). By controlling these parameters to satisfy the equations Da/Ca ≥ 0.65 and Dc/(Ca-Dc) ≥ 0.65, along with controlling electrolyte conductivity (ρ) within 0.008-0.020 S/cm, the patent achieves both high energy density and long cycle life, preventing the deterioration that would normally occur with increased material loading.
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 battery design improves cycle life and service life by optimizing battery parameters, providing a better-performing lithium secondary battery system with improved energy density and cost efficiency.
Implementation Method 1
a positive electrode plate including a positive-electrode current collector and a positive-electrode active material layer arranged on at least one side of the positive-electrode current collector, wherein the positive-electrode active material layer includes a positive-electrode active material Li1+aM1bFe1-cAcP1-dEdO4
Implementation Method 2
the negative-electrode active material layer on the side of the negative electrode plate away from the positive electrode plate has a first lithiation capacity of Ca in mAh/1540.25 mm2
Data Source
AI summary
A lithium secondary battery includes positive and negative electrode plates. The positive-electrode active material layer includes a positive-electrode active material Li1+aM1bFe1-cAcP1-dEdO4 with a mass ratio of not less than 85 wt %. The negative-electrode active material layer includes graphite with a mass ratio of not less than 85 wt %. Areal density, CWc in g/1540.25 mm2, and reversible lithium capacity, Dc in mAh/1540.25 mm2, of the positive-electrode active material layer on one side of the positive electrode plate, reversible lithium capacity, Da in mAh/1540.25 mm2, of the negative-electrode active material layer on the side of the negative electrode plate facing the positive electrode plate, first lithiation capacity, Ca in mAh/1540.25 mm2, of the negative-electrode active material layer on the side of the negative electrode plate away from the positive electrode plate, and conductivity, ρ at 25° C. in S/cm, of the electrolyte solution satisfy equations 1 and 2 described in the disclosure.