Coated NCM Battery Cell Electrolyte for High-Voltage Cycling
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Solution Overview
Problem
Existing secondary batteries face challenges in achieving high energy density and good cycling performance, particularly when operating at high voltages, due to issues such as cation mixing, irreversible phase transitions, and increased internal resistance in nickel-cobalt-manganese ternary materials.
Innovation Solution
A battery cell design featuring a positive electrode active material with a doped nickel-cobalt-manganese inner core coated with a specific element Y, combined with an electrolyte solution containing a first additive with Si-N and Si-O bonds, forms a low-impedance interface film that inhibits LiPF6 decomposition and enhances ion conductivity, and a second additive that reduces acidity and improves thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If nickel-cobalt-manganese ternary material is used as positive electrode active material, then energy density is improved, but structural stability deteriorates during charge-discharge cycling at high voltage
Solution Approach 1:
The patent uses a composite coating layer comprising multiple elements (Al, Ti, B, or Zr) on the nickel-cobalt-manganese ternary material surface. This composite structure combines the high energy density benefits of the ternary material with the structural stability provided by the coating elements, resolving the contradiction between energy density and structural stability during charge-discharge cycling at high voltage.
Solution Approach 2:
The patent applies a localized coating layer on the surface of the positive electrode active material particles. This coating is applied locally to the surface rather than throughout the bulk material, preserving the high energy density properties of the inner nickel-cobalt-manganese ternary material while providing protective qualities at the surface where electrochemical reactions occur.
2Use of energy by moving object
If high voltage operation is implemented, then energy density is improved, but ion conductivity deteriorates due to increased impedance
Solution Approach 1:
The patent modifies the surface composition parameters of the positive electrode active material by introducing specific elements (Al, Ti, B, or Zr) in controlled amounts. This parameter change in the surface composition reduces impedance and improves ion conductivity, allowing high voltage operation without sacrificing reliability.
Solution Approach 2:
The patent employs a thin film coating layer on the surface of the positive electrode active material. This thin film structure provides a low-impedance interface that facilitates ion transport while maintaining the high voltage characteristics needed for high energy density.
3Use of energy by moving object
If high voltage charge-discharge cycling is performed, then energy density is improved, but cycling performance deteriorates due to HF generation and transition metal dissolution
Solution Approach 1:
The coating layer elements (Al, Ti, B, or Zr) act as intermediaries between the electrolyte and the nickel-cobalt-manganese ternary material. They form a protective interface that prevents direct contact between the electrolyte and the transition metals, thereby inhibiting HF generation and metal dissolution during high voltage cycling, which extends cycling performance.
Solution Approach 2:
The patent applies a preliminary protective coating on the positive electrode active material before cycling begins. This pre-formed coating prevents harmful side reactions (HF generation and metal dissolution) from occurring during subsequent high voltage charge-discharge cycles, thereby preserving cycling performance.
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 solution results in a battery cell with both high energy density and improved cycling performance by reducing impedance, inhibiting HF generation, and maintaining structural stability, thereby extending the battery's life and capacity.
Implementation Method 1
The Si-N bond of the first additive is easily bonded to a nucleophilic substance in the electrolyte solution to form a silicon-based derivative
Implementation Method 2
The inner core comprises Li x (Ni a Co b Mn c ) d M e O f A y where M includes one or more of Zr, Sr, B, Ti, Mg, Sn, Tb, W, Nb, Sb, or Al
Data Source
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Figure 3
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AI summary
The present application provides a battery cell, a battery comprising same, and an electrical apparatus. The battery cell comprises a positive electrode plate and an electrolyte solution. The positive electrode plate comprises a positive electrode active material. The positive electrode active material comprises an inner core and a coating layer coating the inner core. The inner core comprises Lix(NiaCobMnc)dMeOfAy, where x, a, b, c, d., e, f, and y are respectively as described in the specification of the present application, M includes one or more of Zr, Sr, B, Ti, Mg, Sn, Tb, W, Nb, Sb, or Al, and A includes one or more of S, N, F, Cl, Br, or I. The coating layer comprises element Y, and the element Y includes one or more of Co, Zr, Sr, B, Ti, Mg, Sn, Tb, W, Nb, Sb, or Al. The electrolyte solution comprises a first additive, and the first additive includes an organic substance comprising a Si-N bond and a Si-O bond.