Energy Storage Device High-Temperature Cycle Stability
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Solution Overview
Problem
Conventional energy storage devices experience significant deterioration in charge-discharge cycle characteristics, particularly at high temperatures and high rates, due to variations in ion path resistance and liquid quantity, leading to reduced discharge capacity retention ratios.
Innovation Solution
The energy storage device incorporates a positive electrode with a Li-Ni-Co-M based composite oxide and a negative electrode containing hardly graphitizable carbon with specific particle diameters, along with an insulating layer between the positive electrode and the separator, to enhance ion path uniformity and suppress oxidative decomposition, thereby maintaining satisfactory cycle characteristics even at high rates and temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a porous insulating layer is provided on the interface between the separator and electrode plate to enhance charge-discharge cycle characteristics, then the discharge capacity retention ratio is improved, but the variation in ion path resistance increases at high temperature and high rate cycles
Solution Approach 1:
The patent changes the material composition parameters of the positive electrode by incorporating specific ratios of Ni, Co, Mn, and other elements in the lithium nickel cobalt manganese oxide compound. This compositional parameter adjustment optimizes the electrode's electrochemical properties, reducing ion path resistance variation while maintaining discharge capacity retention ratio during high temperature and high rate cycles
Solution Approach 2:
The patent uses a composite positive active material consisting of lithium nickel cobalt manganese oxide (LiNi0.8Co0.1Mn0.1O2 or similar compositions) that combines multiple metal oxides. This composite material structure synergistically improves cycle characteristics and stabilizes ion transport properties at elevated temperatures and high charge-discharge rates
2Quantity of substance
If the negative electrode uses graphite with small particle diameter to improve capacity, then the discharge capacity increases, but the ion path resistance increases and cycle characteristics deteriorate at high temperature
Solution Approach 1:
The patent changes the particle size parameter of the negative active material from fine graphite particles to hard carbon particles with D50 diameter of 1.0-6.0 μm. This parameter change reduces ion path resistance and improves charge-discharge kinetics while maintaining adequate capacity, specifically enhancing high rate cycle endurance at high temperatures
Solution Approach 2:
The patent replaces conventional graphite (which has limited high-temperature stability) with hard carbon material that, while having slightly lower theoretical capacity, provides superior stability and longevity in high temperature and high rate cycle conditions, effectively trading some capacity for improved reliability
3Quantity of substance
If the positive electrode contains high Ni content to increase capacity, then the discharge capacity increases, but the oxidative decomposition of the electrolyte increases
Solution Approach 1:
The patent employs a composite cathode material LiNi0.8Co0.1Mn0.1O2 (or similar high-Ni compositions) where nickel provides high capacity while cobalt and manganese components suppress oxidative decomposition of the electrolyte. This composite structure allows high Ni content (0.7-0.9) while maintaining electrolyte stability through the synergistic effects of multiple metal oxides
Solution Approach 2:
The patent applies surface modification or coating treatments on the positive electrode particles to create a protective layer that locally prevents contact between the high-Ni active material and the electrolyte, thereby suppressing oxidative decomposition at the particle surface while maintaining high capacity in the bulk material
Data Source
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AI summary
An energy storage device comprising: a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, a nonaqueous electrolyte, and an insulating layer disposed between the positive electrode and the separator, wherein the positive electrode contains a compound represented by LiaNibCocMdWxNbyZrzO2 (provided that a, b, c, d, x, y and z satisfy the equations of 0 ≤ a ≤ 1.2, 0 ≤ b ≤ 1, 0.1 ≤ c ≤ 0.4, 0 ≤ d ≤ 0.5, 0 ≤ x ≤ 0.1, 0 ≤ y ≤ 0.1, 0 ≤ z ≤ 0.1 and b + c + d = 1, and M denotes at least one kind of element selected from the group consisting of Mn, Ti, Cr, Fe, Co, Cu, Zn, Al, Ge, Sn and Mg) as a positive active material and the negative electrode contains hardly graphitizable carbon with a D50 particle diameter greater than or equal to 1.0 µm and less than or equal to 6.0 µm as a negative active material.