Lithium Secondary Battery Electrode Balancing for Long Cycle Life
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Solution Overview
Problem
The service lives of lithium secondary batteries need to be prolonged to meet user demands for improved battery performance, while maintaining capacity and energy density.
Innovation Solution
Optimizing the design parameters of lithium secondary batteries by adjusting the lithium content and reversible capacity on the electrode surfaces, using specific positive and negative electrode materials, and incorporating conductive agents and binders to enhance conductivity and stability, along with a suitable electrolyte and separator configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the battery uses conventional electrode materials and fixed design parameters, then the manufacturing process is simple, but the service life is insufficient to meet user demands
Solution Approach 1:
The patent applies parameter changes by optimizing specific design parameters including the ratio of positive to negative electrode plate areas (0.95-1.05), lithium content per unit area (Wa: 5-10 g/m², Wc: 3-8 g/m²), and thickness ratios (1.0-1.5). These parameter adjustments resolve the contradiction by achieving extended service life (exceeding 6000 cycles at 80% capacity retention) while maintaining manageable manufacturing complexity through defined parameter ranges.
2Reliability
If the battery optimizes for longer service life through parameter adjustment, then the service life is prolonged, but the capacity and energy density must not be remarkably reduced
Solution Approach 1:
The patent resolves this contradiction through precise parameter changes that balance service life and capacity. The positive electrode uses lithium iron phosphate (90-95 wt%) or lithium nickel cobalt manganese oxide (85-90 wt%) with controlled lithium content (Wa: 5-10 g/m²), while the negative electrode uses graphite (95-99 wt%) with lithium content (Wc: 3-8 g/m²). These parameters achieve service life exceeding 6000 cycles at 80% capacity retention while maintaining high initial capacity and energy density.
Solution Approach 2:
The patent employs composite materials to simultaneously achieve long service life and high capacity. The positive electrode combines lithium iron phosphate or lithium nickel cobalt manganese oxide with conductive agents (5-10 wt%) and binders (5-10 wt%). The negative electrode uses graphite composite with similar additives. This composite approach enables the battery to withstand 6000+ cycles while preserving high capacity and energy density.
3Quantity of substance
If the battery uses high content of positive electrode active materials (≥94%), then the capacity and energy density are improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent resolves this contradiction by defining specific parameter ranges for active material content. The positive electrode requires 94-97 wt% active materials (lithium iron phosphate or lithium nickel cobalt manganese oxide), while the negative electrode requires 96-99 wt% graphite. These standardized parameter ranges enable manufacturing precision to be maintained through controlled formulation processes, achieving high capacity and energy density without excessive manufacturing complexity.
Data Source
AI summary
A lithium secondary battery includes a positive electrode plate and a negative electrode plate; the lithium content per unit area on a single side surface of the positive electrode plate is denoted as Wa in g/m2; the lithium content per unit area on a single side surface of the negative electrode plate is denoted as Wc in g/m2; the reversible capacity per unit area on the surface of the side of the negative electrode plate facing towards the positive electrode plate is denoted as Da in mAh/m2; the first lithiation capacity per unit area on the surface of the side of the negative electrode plate facing away from the positive electrode plate is denoted as Ca in mAh/m2; and the lithium secondary battery meets the following conditions:70%≤C1×(Wa+Wc)Da≤90%,and/or,63%≤C1×(Wa+Wc)Ca≤81%,wherein C1 is the theoretical capacity, 3,861 mAh/g, of lithium metal.